Terminal and communication method

ABSTRACT

A terminal (1050) includes a light receiver (151) that receives a light signal emitted by an apparatus (1000), the light signal including an identifier (SSID) of at least one base station (470); a receiver receiver (153) that performs a reception process on the received light signal to output reception data; a data analyzer (155) that selects one base station based on the identifier of the at least one base station that is included in the reception data; and a radio device (453) that establishes a wireless connection with the selected base station (470) by using the identifier of the base station (470) and wirelessly communicates with the base station (470).

TECHNICAL FIELD

The present disclosure relates to a terminal and a communication method.

BACKGROUND ART

A method using the Global Positioning System (GPS) is available as amethod in which a terminal obtains information on the location or thelike of the terminal. In the method using the GPS, the terminal receivesa modulated signal transmitted by a satellite and performs positioningcalculation, thereby estimating the location of the terminal. However,when it is difficult for the terminal to receive a radio wavetransmitted by the satellite (for example, when the terminal is locatedindoors), it is difficult for the terminal to estimate its location.

As a method in which the terminal estimates its location in such a case,there is a method in which the terminal estimates information on itslocation or the like by using a radio wave transmitted by an accesspoint (AP) of a wireless local area network (LAN), for example, asdisclosed in NPL 1.

CITATION LIST Non Patent Literature

NPL 1: “NGP use case document”, IEEE 802.11-16/0137r4, March 2016

SUMMARY OF INVENTION

However, it is not easy for the terminal to obtain a service setidentifier (SSID) of an access point that is safely accessible. Thus,there is a possibility that, when the terminal attempts to obtaininformation on its location or the like, the terminal may connect to anaccess point having an unsafe SSID, leading to a threat of informationleakage or the like.

An embodiment of the present disclosure contributes to providing aterminal and a communication method that enable a terminal to safelyobtain information.

A terminal according to an embodiment of the present disclosureincludes: a light receiver that receives a light signal emitted by atransmitter, the light signal including an identifier of at least onebase station; a data analyzing circuit that selects one base stationbased on the identifier of the at least one base station that isincluded in the received light signal; and a radio device thatestablishes a wireless connection with the selected base station byusing the identifier of the base station and wirelessly communicateswith the base station.

A communication method according to an embodiment of the presentdisclosure includes: receiving a light signal emitted by a transmitter,the light signal including an identifier of at least one base station;selecting one base station based on the identifier of the at least onebase station that is included in the received light signal; andestablishing a wireless connection with the selected base station byusing the identifier of the base station and wirelessly communicatingwith the base station.

It should be noted that general or specific embodiments may beimplemented as a system, a method, an integrated circuit, a computerprogram, a recording medium, or any selective combination thereof.

According to an embodiment of the present disclosure, the terminal isable to safely obtain information.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram for describing the principle of line-scan sampling.

FIG. 2 is a diagram illustrating an example of a captured image when anexposure period is long.

FIG. 3 is a diagram illustrating an example of a captured image when anexposure period is short.

FIG. 4A is a diagram for describing 4 PPM.

FIG. 4B is a diagram for describing Manchester coding.

FIG. 5 is a diagram illustrating an example configuration of a visiblelight communication system.

FIG. 6 is a diagram illustrating an example configuration of acommunication system according to Embodiment 1.

FIG. 7 is a diagram illustrating an example frame configurationaccording to Embodiment 1.

FIG. 8 is a diagram illustrating a positional relationship betweenapparatuses and a terminal according to Embodiment 2.

FIG. 9 is a diagram illustrating an example configuration of acommunication system according to Embodiment 3.

FIG. 10 is a diagram illustrating a display example of a displayaccording to Embodiment 3.

FIG. 11 is a diagram illustrating an example frame configuration of amodulated signal transmitted by a first apparatus according toEmbodiment 3.

FIG. 12 is a diagram illustrating an example frame configuration of amodulated signal transmitted by a base station according to Embodiment3.

FIG. 13 is a flowchart illustrating an example process in thecommunication system according to Embodiment 3.

FIG. 14 is a diagram illustrating a display example of the displayaccording to Embodiment 3.

FIG. 15 is a diagram illustrating an example configuration of acommunication system according to Embodiment 4.

FIG. 16 is a diagram illustrating an example frame configuration of amodulated signal transmitted by a first apparatus according toEmbodiment 4.

FIG. 17 is a diagram illustrating an example frame configuration of amodulated signal transmitted by a radio device of a terminal accordingto Embodiment 4.

FIG. 18 is a flowchart illustrating an example process in thecommunication system according to Embodiment 4.

FIG. 19 is a diagram illustrating an example configuration of acommunication system according to Embodiment 5.

FIG. 20 is a diagram illustrating an example frame configuration of amodulated signal including an SSID and transmitted by a third apparatusaccording to Embodiment 5.

FIG. 21 is a diagram illustrating an example frame configuration of amodulated signal including an encryption key and transmitted by thethird apparatus according to Embodiment 5.

FIG. 22 is a flowchart illustrating an example process in thecommunication system according to Embodiment 5.

FIG. 23 is a flowchart illustrating another example process in thecommunication system according to Embodiment 5.

FIG. 24 is a diagram illustrating an example of a space in which thecommunication system according to Embodiment 5 is disposed.

FIG. 25 is a diagram illustrating an example configuration of acommunication system according to Embodiment 6.

FIG. 26 is a flowchart illustrating an example process in thecommunication system according to Embodiment 6.

FIG. 27 is a diagram illustrating an example configuration of acommunication system according to Embodiment 7.

FIG. 28 is a diagram illustrating an example frame configuration of amodulated signal transmitted by a fifth apparatus according toEmbodiment 7.

FIG. 29 is a diagram illustrating an example frame configuration of amodulated signal transmitted by the fifth apparatus according toEmbodiment 7.

FIG. 30 is a diagram illustrating an example frame configuration of amodulated signal transmitted by the fifth apparatus according toEmbodiment 7.

FIG. 31 is a diagram illustrating an example of a frame transmissionmethod by the fifth apparatus according to Embodiment 7.

FIG. 32 is a diagram illustrating an example of a space in which thecommunication system according to Embodiment 7 is disposed.

FIG. 33 is a flowchart illustrating an example process in thecommunication system according to Embodiment 7.

FIG. 34 is a diagram illustrating an example of an AP connection methodaccording to Embodiment 8 (Application Example 1).

FIG. 35 is a diagram illustrating an example of an AP connection methodaccording to Embodiment 8 (Application Example 2).

FIG. 36A is a diagram illustrating a display example of a display of aterminal according to Embodiment 8.

FIG. 36B is a diagram illustrating another display example of thedisplay of the terminal according to Embodiment 8.

FIG. 37 is a diagram illustrating an example configuration of acommunication system within an aircraft and an outside network accordingto Embodiment 8.

FIG. 38 is a diagram illustrating an example configuration of anothercommunication system that performs visible light communication.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a detailed description will be given of embodiments of thepresent disclosure with reference to the drawings.

[Modulation/Demodulation Method in Visible Light Communication]

In the present embodiment, a visible light communication scheme is usedin which a modulated signal is transmitted/received as a visible lightsignal.

First, an outline of the visible light communication scheme will bespecifically described.

<Line-Scan Sampling>

A smartphone, a digital camera, or the like includes an image sensor,such as a complementary metal oxide semiconductor (CMOS) sensor, mountedtherein. In an image captured by the CMOS sensor, the entire portionthereof does not strictly express a scene of the same time, but anamount of light received by the sensor is read out for each line. Thus,control is performed to start and finish receiving light with a time lagfor each line, with the time required for reading being taken intoconsideration. That is, an image captured by the CMOS sensor is made upof many lines with slight time lags.

The visible light communication scheme used in the present embodimentutilizes the properties of the CMOS sensor and realizes higher speed inreceiving a visible light signal. That is, in the visible lightcommunication scheme, with use of a characteristic that an exposureperiod slightly varies among lines, the brightness and color of a lightsource at a plurality of time points can be measured for each line froma single image (an image captured by the image sensor), as illustratedin FIG. 1, and a signal modulated at a speed higher than a frame ratecan be captured.

Hereinafter, this sampling method is referred to as “line-scansampling”, and a line of pixels exposed to light at the same timing isreferred to as an “exposed line”.

Note that, in an image capturing setting at the time of capturing animage with a camera function (a video or still image shooting function),even if a light source flashing at high speed (pulse lighting) isphotographed, the flash does not appear as a striped pattern alongexposed lines. This is because, in this setting, an exposure period ismuch longer than a flash cycle (pulse width) of the light source, andthus, as illustrated in FIG. 2, changes in brightness resulting from theflash (emission pattern) of the light source are equalized and adifference in pixel values between exposed lines becomes very small, sothat a substantially uniform image is created.

In contrast, as illustrated in FIG. 3, when an exposure period is set toa value substantially corresponding to the flash cycle of the lightsource, the flash state (emission pattern) of the light source can beobserved as changes in brightness of exposure lines.

For example, an exposed line is designed so as to be parallel with thelongitudinal direction of the image sensor. In this case, when it isassumed that the frame rate is 30 frames per second (fps), for example,32400 or more samples per second are obtained at a resolution of1920×1080, and 64800 or more samples per second are obtained at aresolution of 3840×2160.

<Light Source and Modulation Scheme>

In visible light communication, a light emitting diode (LED) can be usedas a transmitter, for example. The LED has been becoming common aslighting or a back light source of a display and can be caused to flashat high speed.

However, it is not always possible to cause the light source used as atransmitter in visible light communication to freely flash for visiblelight communication. If flash in visible light communication is visuallyperceived by a human, an original function of the light source, such asa lighting function, is impaired. Thus, a transmission signal isrequired to be as bright as possible such that flash thereof is notperceived by the eyes of a human.

As a modulation scheme responding to such a requirement, a modulationscheme called 4-pulse position modulation (4 PPM) is available, forexample. 4 PPM is a scheme of expressing two bits by using a combinationof four light or dark states of a light source, as illustrated in FIG.4A. In 4 PPM, three states among four states are light and the remainingone state is dark, as illustrated in FIG. 4A. Thus, an averagebrightness is ¾=75% regardless of the content of a signal.

For comparison, Manchester coding illustrated in FIG. 4B is available asa similar scheme. Manchester coding is a scheme of expressing one bit byusing two states. The modulation efficiency is 50%, which is the same asin 4 PPM. However, one of the two states is light and the other is dark,and thus an average brightness is ½=50%. That is, 4 PPM is moreappropriate than Manchester coding as a modulation scheme in visiblelight communication.

<Example of Overall Configuration of Communication System>

As illustrated in FIG. 5, a communication system for performing visiblelight communication includes at least a transmitter that transmits(emits) a light signal and a receiver that receives the light signal.For example, there are two types of transmitters, a variable lighttransmitter that changes the light to be transmitted in accordance withvideo or content to be displayed, and a fixed light transmitter thatcontinues transmitting fixed light.

The receiver receives the light signal from the transmitter, and is ableto obtain related information associated with the light signal and toprovide the related information to a user, for example.

An outline of the visible light communication scheme has been describedabove. A communication scheme applicable to optical communicationdescribed in the following embodiments is not limited to theabove-described scheme. For example, a light emitting unit of atransmitter may transmit data by using a plurality of light sources. Areceiver of a receiving device need not necessarily be an image sensor,such as a CMOS sensor, and may adopt, for example, a communicationscheme in which a device capable of converting a light signal into anelectric signal, such as a photodiode, can be used. In this case, it isnot necessary to perform sampling by using the above-described line-scansampling, and thus even a scheme requiring sampling of 32400 or moresamples per second is applicable. Depending on application, acommunication scheme using a radio wave of frequencies other than thoseof visible light, such as infrared light or ultraviolet light, may beused.

Embodiment 1

FIG. 6 illustrates an example of the configurations of an apparatus 100and a terminal 150 in the present embodiment.

[Configuration of Apparatus 100]

The apparatus 100 (corresponding to the transmitter in visible lightcommunication) includes a visible light source, a lighting device, or alight (collectively referred to as a light source), such as a lightemitting diode (LED). Hereinafter, the apparatus 100 may be referred toas a “first apparatus”.

In the first apparatus 100 in FIG. 6, a transmitter 102 receives, forexample, location-related or position-related information 101 as input.The transmitter 102 may receive time-related information 105 as input.The transmitter 102 may receive both the location-related orposition-related information 101 and the time-related information 105 asinput.

The transmitter 102 receives the location-related or position-relatedinformation 101 and/or the time-related information 105 as input,generates a (light) modulated signal 103 based on these input signals,and outputs the modulated signal 103. Subsequently, the modulated signal103 is transmitted from, for example, a light source 104.

Now, a description will be given of examples of the location-related orposition-related information 101.

Example 1

The location-related or position-related information 101 may beinformation on the latitude and/or the longitude of a location orposition. For example, information “latitude 45° N, longitude 135° E”may be used as the location-related or position-related information 101.

Example 2

The location-related or position-related information 101 may beinformation on an address. For example, information “1-1-1, X town,Chiyoda-ku, Tokyo” may be used as the location-related orposition-related information 101.

Example 3

The location-related or position-related information 101 may beinformation on a building or facility. For example, information “Tokyotower”, may be used as the location-related or position-relatedinformation 101.

Example 4

The location-related or position-related information 101 may beinformation about a location or position peculiar to something installedin a building or facility.

For example, it is assumed that there are spaces for parking five carsin a parking lot. In this case, a first parking space is called A-1, asecond parking space is called A-2, a third parking space is called A-3,a fourth parking space is called A-4, and a fifth parking space iscalled A-5. In this case, for example, information “A-3” may be used asthe location-related or position-related information 101.

Such an example is not limited to the case of a parking lot. Forexample, information about “areas, seats, shops, facilities, etc.” in aconcert hall, a stadium for baseball, soccer, tennis, or the like, anaircraft, a lounge in an airport, a train, a station, or the like may beused as the location-related or position-related information 101.

Examples of the location-related or position-related information 101have been described above. The configuration of the location-related orposition-related information 101 is not limited to the above-describedexamples.

[Configuration of Terminal 150]

The terminal 150 (corresponding to the receiver in visible lightcommunication) in FIG. 6 receives the modulated signal 103 transmittedby the first apparatus 100.

A light receiver (light receiving device) 151 is, for example, an imagesensor, such as a complementary metal oxide semiconductor (CMOS) sensoror an organic CMOS sensor. The light receiver 151 receives lightincluding the modulated signal transmitted by the first apparatus 100and outputs a reception signal 152.

The reception signal 152 output from the light receiver 151 may be asignal including information on an image or a video captured by theimage sensor, or may be a signal output from another element thatperforms photoelectric conversion (that converts light into an electricsignal). Hereinafter, when a description is given indicating that adevice on the reception side receives a modulated signal without anyspecific explanation about a process performed by the light receiver151, it means that the device on the reception side is the lightreceiver 151 and that photoelectric conversion (conversion from lightinto an electric signal) is performed on light including the modulatedsignal to obtain “a signal of an image or a video” and “a modulatedsignal for transmitting information”. However, the above-describedmethod is an example of a method in which the device on the receptionside receives a modulated signal, and a method for receiving a modulatedsignal is not limited thereto.

A receiver 153 receives the reception signal 152 as input, performsprocessing, such as demodulation and error-correction decoding, on themodulated signal included in the reception signal 152, and outputsreception data 154.

A data analyzer 155 receives the reception data 154 as input, analyzesthe reception data 154 to estimate the location/position of the terminal150, for example, and outputs information 156 including at leastlocation/position information on the terminal 150.

A display 157 receives the information 156 as input, and displays thelocation/position of the terminal 150 by using the location/positioninformation on the terminal 150 included in the information 156.

[Frame Configuration]

FIG. 7 illustrates an example of the frame configuration of themodulated signal transmitted by the first apparatus 100.

In FIG. 7, the horizontal axis indicates time. The first apparatus 100transmits, for example, a preamble 201, and then transmits a controlinformation symbol 202, alocation-information-or-position-information-related symbol 203, and atime-information-related symbol 204.

The preamble 201 is a symbol by which the terminal 150 that receives themodulated signal transmitted by the first apparatus 100 performs, forexample, signal detection, time synchronization, frame synchronization,and the like.

The control information symbol 202 is a symbol including, for example,data representing a method for configuring the modulated signal, amethod of an error-correction coding scheme that is used, a method forconfiguring the frame, and the like.

The location-information-or-position-information-related symbol 203 is asymbol including the location-related or position-related information101 illustrated in FIG. 6.

The frame may include a symbol other than the symbols 201, 202, and 203.For example, the frame may include the time-information-related symbol204, as illustrated in FIG. 7. The time-information-related symbol 204includes, for example, the time-related information 105 indicating thetime when the first apparatus 100 transmits the modulated signal. Theconfiguration of the frame of the modulated signal transmitted by thefirst apparatus 100 is not limited to that illustrated in FIG. 7, andthe symbols included in the modulated signal are not limited to thoseillustrated in FIG. 7. The frame may include a symbol including otherdata/information.

[Advantages]

A description will be given of advantages that may be obtained when thefirst apparatus 100 transmits a modulated signal and the terminal 150receives the modulated signal, as described above with reference toFIGS. 6 and 7.

The first apparatus 100 transmits a modulated signal by using visiblelight, and thus the terminal 150 capable of receiving the modulatedsignal is not so far from the location of the first apparatus 100. Thus,by obtaining location/position information transmitted by the firstapparatus 100, the terminal 150 is able to easily obtain highly accurateposition information (without performing complicated signal processing).

In addition, as a result of installing the first apparatus 100 at alocation where a radio wave from a GPS satellite is difficult toreceive, the terminal 150 is able to safely obtain highly accurateposition information by receiving a modulated signal transmitted by thefirst apparatus 100 even in a situation where it is difficult to receivea radio wave from the GPS satellite.

Embodiment 2

In the present embodiment, a description will be given of a case wherethere are a plurality of first apparatuses 100, each being the onedescribed in Embodiment 1.

In the present embodiment, for example, a first first apparatus 301-1having a configuration similar to that of the first apparatus 100illustrated in FIG. 6 transmits a modulated signal, as illustrated inFIG. 8. A terminal 302 having a configuration similar to that of theterminal 150 illustrated in FIG. 6 receives the modulated signaltransmitted by the first first apparatus 301-1 and obtains, for example,first first location/position-related information and first firsttime-related information.

Likewise, a second first apparatus 301-2 having a configuration similarto that of the first apparatus 100 illustrated in FIG. 6 transmits amodulated signal. The terminal 302 receives the modulated signaltransmitted by the second first apparatus 301-2 and obtains, forexample, second first location/position-related information and secondfirst time-related information.

The terminal 302 is cable of calculating the distance between the firstfirst apparatus 301-1 and the second first apparatus 301-2 in FIG. 8 byusing the first first location/position-related information and thesecond first location/position-related information. In addition, theterminal 302 is cable of calculating the distance between the terminal302 and the first first apparatus 301-1 based on the first firsttime-related information and, for example, the time when the terminal302 receives the modulated signal transmitted by the first firstapparatus 301-1. Likewise, the terminal 302 is cable of calculating thedistance between the terminal 302 and the second first apparatus 301-2based on the second first time-related information and, for example, thetime when the terminal 302 receives the modulated signal transmitted bythe second first apparatus 301-2.

The terminal 302 learns the position of the first first apparatus 301-1from the first first location/position-related information. The terminal302 learns the position of the second first apparatus 301-2 from thesecond first location/position-related information.

The terminal 302 learns “a triangle formed by the first first apparatus301-1, the second first apparatus 301-2, and the terminal 302” from “thedistance between the first first apparatus 301-1 and the second firstapparatus 301-2”, “the distance between the first first apparatus 301-1and the terminal 302”, and “the distance between the second firstapparatus 301-2 and the terminal 302”.

Thus, the terminal 302 is cable of accurately calculating and obtainingthe position of the terminal 302 based on “the position of the firstfirst apparatus 301-1”, “the position of the second first apparatus301-2”, and “the triangle formed by the first first apparatus 301-1, thesecond first apparatus 301-2, and the terminal 302”.

Note that a geodetic surveying method in which the terminal 302 obtainslocation/position information is not limited to that described above,and any other method may be used for geodetic surveying. Examples of thegeodetic surveying method include triangulation, traversing,trilateration, and leveling.

As described above, in the present embodiment, the terminal 302 obtainsthe above-described information from the plurality of apparatuses 301each including a light source for transmitting location information,thereby being able to estimate the position of the terminal 302 withhigh accuracy.

In the present embodiment, as described in Embodiment 1, as a result ofinstalling the apparatus 301 including a light source that transmitslocation information at a location where a radio wave from a GPSsatellite is difficult to receive, the terminal 302 is able to safelyobtain highly accurate position information by receiving a modulatedsignal transmitted by the apparatus 301 even in a situation where it isdifficult to receive a radio wave from the GPS satellite.

In the above-described example, the terminal 302 receives the modulatedsignals transmitted by the two apparatuses 301. The operation can besimilarly performed when the terminal 302 receives modulated signalstransmitted by three or more apparatuses 301. As the number ofapparatuses 301 increases, the accuracy with which the terminal 302calculates position information increases advantageously.

Embodiment 3

FIG. 9 illustrates an example of the configurations of an apparatus 400,a terminal 450, and a base station 470 (or an access point (AP)) thatcommunicates with the terminal 450 in the present embodiment.

The apparatus 400 includes, for example, a visible light source, alighting device, a light source, or a light, such as an LED.Hereinafter, the apparatus 400 may be referred to as a “firstapparatus”.

In the first apparatus 400 illustrated in FIG. 9, the components thatoperate similarly to those of the first apparatus 100 illustrated inFIG. 6 are denoted by the same numerals. In the terminal 450 illustratedin FIG. 9, the components that operate similarly to those of theterminal 150 illustrated in FIG. 6 are denoted by the same numerals.

In the first apparatus 400 in FIG. 9, the transmitter 102 receives, forexample, the location-related or position-related information 101,service set identifier (SSID)-related information 401-1, which is anidentifier of the base station 470, and access-destination-relatedinformation 401-2 as input. In addition, the transmitter 102 may receivethe time-related information 105 as input.

The transmitter 102 receives the location-related or position-relatedinformation 101, the SSID-related information 401-1, and theaccess-destination-related information 401-2, and/or the time-relatedinformation 105 as input, generates the (light) modulated signal 103based on these input signals, and outputs the modulated signal 103. Themodulated signal 103 is transmitted, for example, from the light source104.

Examples of the location-related or position-related information 101have been described in Embodiment 1, and thus the description thereof isomitted here.

Next, a description will be given of the SSID-related information 401-1and the access-destination-related information 401-2.

First, a description will be given of the SSID-related information401-1.

The SSID-related information 401-1 is information indicating the SSID ofthe base station 470 in FIG. 9. Here, when it is determined that theSSID notified of using a light signal is the SSID of a safe basestation, the first apparatus 400 is able to provide the terminal 450with access to the base station 470, which is a safe access destination.Accordingly, the terminal 450 in FIG. 9 is able to safely obtaininformation from the base station 470.

On the other hand, the first apparatus 400 is able to limit the terminalthat accesses the base station 470 to a terminal positioned in a spacewhere a light signal transmitted (emitted) by the first apparatus 400can be received.

When the terminal 450 receives a light signal transmitted in apredetermined scheme, the terminal 450 may determine that the notifiedSSID is the SSID of a safe base station. The terminal 450 may separatelyperform a process of determining whether or not the notified SSID issafe. For example, the first apparatus 400 may transmit a light signalincluding a predetermined identifier, and the terminal 450 maydetermine, based on the received identifier, whether or not the notifiedSSID is the SSID of a safe base station. The terminal 450 does notnecessarily perform the process of determining whether or not the basestation is safe. With use of the characteristics of visible light, auser may select a safe first apparatus 400, and the terminal 450 mayreceive a light signal from the first apparatus 400 to obtain the SSIDof a safe base station.

FIG. 9 illustrates a single base station 470. Also when one or more basestations (or APs) other than the base station 470 exist, the terminal450 accesses the base station 470 by using an SSID obtained from thefirst apparatus 400 and obtains information.

Next, a description will be given of the access-destination-relatedinformation 401-2.

The access-destination-related information 401-2 is information about anaccess destination from which the terminal 450 obtains information afteraccessing the base station 470. A specific operation example of thepresent embodiment will be described below.

The SSID-related information 401-1 and the access-destination-relatedinformation 401-2 have been described above.

The terminal 450 receives the modulated signal 103 transmitted by thefirst apparatus 400.

The light receiver 151 is, for example, an image sensor, such as a CMOSsensor or an organic CMOS sensor. The light receiver 151 receives lightincluding a modulated signal transmitted by the first apparatus 400 andoutputs the reception signal 152.

The receiver 153 receives the reception signal 152 received by the lightreceiver 151 as input, performs processing, such as demodulation anderror-correction decoding, on the modulated signal included in thereception signal 152, and outputs the reception data 154.

The data analyzer 155 receives the reception data 154 as input, andestimates, for example, the location/position of the terminal 450 fromthe reception data 154. Subsequently, the data analyzer 155 outputs theinformation 156 including at least the location/position information onthe terminal 450, SSID-related information 451, andaccess-destination-related information 452.

The display 157 receives the information 156 including thelocation/position information on the terminal 450, the SSID-relatedinformation 451, and the access-destination-related information 452 asinput, and displays, for example, the location/position of the terminal450, the SSID of a communication partner that a radio device 453included in the terminal 450 is to access, and/or an access destination(hereinafter, this display operation is referred to as a “first displayoperation”).

For example, after the first display operation, the radio device 453receives the SSID-related information 451 and theaccess-destination-related information 452 as input. Subsequently, theradio device 453 establishes a connection with the communication partnerby using, for example, a radio wave based on the SSID-relatedinformation 451. In the case of FIG. 9, the radio device 453 establishesa connection with the base station 470.

Subsequently, the radio device 453 generates a modulated signal fromdata including information about the access destination based on theaccess-destination-related information 452, and transmits the modulatedsignal to the base station 470 by using, for example, a radio wave.

In FIG. 9, the base station 470, which is the communication partner ofthe terminal 450, receives the modulated signal transmitted by the radiodevice 453 included in the terminal 450.

Subsequently, the base station 470 performs processing, such asdemodulation and error-correction decoding, on the received modulatedsignal, and outputs reception data 471 including the information on theaccess destination transmitted by the terminal 450. The base station 470accesses a desired access destination via a network based on theinformation on the access destination, and, for example, obtains desiredinformation 472 from the access destination. The base station 470receives the desired information 472 as input, generates a modulatedsignal from the desired information 472, and transmits the modulatedsignal to the terminal 450 (the radio device 453) by using, for example,a radio wave.

The radio device 453 of the terminal 450 receives the modulated signaltransmitted by the base station 470, performs processing, such asdemodulation and error-correction decoding, and obtains the desiredinformation 472.

For example, it is assumed that the desired information 472 is a map, amap/floor guide of a building, a map/floor guide of a facility, amap/floor guide of a parking lot, or information on “areas, seats,shops, and facilities” in a concert hall, a stadium, an aircraft, alounge in an airport, a train, a station, or the like.

The display 157 receives information 454 including the desiredinformation 472, the information 156 including at least thelocation/position information on the terminal 450, and the SSID-relatedinformation 451 as input. After the first display operation, the display157 performs display while mapping the position of the terminal 450 on amap, floor guide, information on a facility, information on seats, orinformation on shops, based on the desired information 472 and theinformation 156 including at least the location/position information onthe terminal 450.

FIG. 10 illustrates a specific display example of the display 157.

The display in FIG. 10 shows a “third floor”. Each of A-1, A-2, A-3,A-4, A-21, A-22, A-23, and A-24 denotes the position of a parking spacefor a car. Each of B-1 and B-2 denotes the position of an elevator. Theinformation on a map including the positions of the parking spaces andthe elevators is an example of the desired information 454 (472).

As illustrated in FIG. 10, the display 157 displays the current positionof the terminal 450 while mapping it on the map. The current position isinformation that is obtained from the information 156 including at leastthe location/position information on the terminal 450.

FIG. 11 illustrates an example of the frame configuration of themodulated signal transmitted by the first apparatus 400 illustrated inFIG. 9. In FIG. 11, the horizontal axis indicates time. In FIG. 11, thesymbols for transmitting information similar to that in FIG. 7 aredenoted by the same numerals, and the description thereof is omitted.

The first apparatus 400 transmits an SSID-related symbol 600-1 and anaccess-destination-related symbol 600-2, in addition to the preamble201, the control information symbol 202, thelocation-information-or-position-information-related symbol 203, and thetime-information-related symbol 204.

The SSID-related symbol 600-1 is a symbol for transmitting theSSID-related information 401-1 in FIG. 9, and theaccess-destination-related symbol 600-2 is a symbol for transmitting theaccess-destination-related information 401-2 in FIG. 9. The frame inFIG. 11 may include a symbol other than the symbols illustrated in FIG.11. The frame configuration, including the order in which the symbolsare transmitted, is not limited to the configuration in FIG. 11.

FIG. 12 illustrates an example of the frame configuration of themodulated signal transmitted by the base station 470 illustrated in FIG.9. In FIG. 12, the horizontal axis indicates time.

As illustrated in FIG. 12, the base station 470 transmits, for example,a preamble 701, and then transmits a control information symbol 702 andan information symbol 703.

The preamble 701 is a symbol by which the terminal 450 that receives themodulated signal transmitted by the base station 470 performs, forexample, signal detection, time synchronization, frame synchronization,frequency synchronization, frequency offset estimation, and the like.

The control information symbol 702 is a symbol including, for example,data of information about an error-correction coding scheme and amodulation scheme that are used to generate the modulated signal, andinformation about the frame configuration. The radio device 453 of theterminal 450 performs demodulation or the like on the modulated signalbased on the information of the control information symbol 702.

The information symbol 703 is a symbol for transmitting information. Inthe present embodiment, the information symbol 703 is a symbol fortransmitting the desired information 472 described above.

The base station 470 illustrated in FIG. 9 may transmit a frameincluding a symbol other than the symbols illustrated in FIG. 12. Forexample, the base station 470 may transmit a frame in which a pilotsymbol (reference symbol) is included in a middle of the informationsymbol 703. The frame configuration, including the order in which thesymbols are transmitted, is not limited to the configuration in FIG. 12.In FIG. 12, a plurality of symbols may exist in the frequency axisdirection. That is, symbols may exist at a plurality of frequencies (aplurality of carriers) in FIG. 12.

In addition, for example, the modulated signal that is transmitted bythe first apparatus 400 and that has the frame configuration illustratedin FIG. 11 may be repeatedly transmitted at a regular interval, forexample. Accordingly, a plurality of terminals 450 are able to performthe above-described operation.

FIG. 13 is a flowchart illustrating an example of a process performed bythe “first apparatus 400”, the “terminal 450”, and the “base station470” illustrated in FIG. 9 described above.

First, the first apparatus 400 transmits a modulated signal having theframe configuration illustrated in FIG. 11 (ST801).

Subsequently, the terminal 450 receives the modulated signal transmittedby the first apparatus 400 and estimates the location/position of theterminal 450 (ST802).

Also, the terminal 450 receives the modulated signal transmitted by thefirst apparatus 400 and obtains the SSID of the base station 470 thatthe terminal 450 is to access (ST803).

Subsequently, the terminal 450 transmits, to the base station 470, amodulated signal including data including the access-destination-relatedinformation 452 for obtaining information, such as a map, by using aradio wave, for example (ST804).

The base station 470 receives the modulated signal transmitted by theterminal 450, obtains information on the access destination, accesses adesired access destination via a network, and obtains desiredinformation, such as a map (the information to be transmitted to theterminal 450) (ST805).

Subsequently, the base station 470 transmits a modulated signalincluding the obtained desired information, such as a map, to theterminal 450 by using, for example, a radio wave (ST806).

The terminal 450 receives the modulated signal transmitted by the basestation 470 and obtains information, such as a map. Subsequently, theterminal 450 performs display illustrated in FIG. 10 based on theinformation, such as a map, and the already obtained location/positioninformation on the terminal 450 (ST807).

Next, a description will be given of an operation example in a casewhere a plurality of first apparatuses 400 and the base station 470 areinstalled in the location illustrated in FIG. 10.

FIG. 14 illustrates a map of a location similar to that in FIG. 10. Thatis, FIG. 14 illustrates a map of the “third floor” as described in FIG.10. In FIG. 14, A-1, A-2, A-3, A-4, A-21, A-22, A-23, and A-24 denoteparking spaces for cars, and B-1 and B-2 denote elevators.

At the position of a single circle 901-1 in FIG. 14, a first apparatushaving a configuration similar to that of the first apparatus 400illustrated in FIG. 9 is installed. Hereinafter, the first apparatushaving a configuration similar to that of the first apparatus 400 andinstalled at the position denoted by 901-1 will be referred to as a“first first apparatus 400”. The first first apparatus 400 hasinformation “A-1” as location-related information or position-relatedinformation, and transmits the information “A-1”.

At the position of a single circle 901-2 in FIG. 14, a first apparatushaving a configuration similar to that of the first apparatus 400 inFIG. 9 is installed. Hereinafter, the first apparatus having aconfiguration similar to that of the first apparatus 400 and installedat the position denoted by 901-2 will be referred to as a “second firstapparatus 400”. The second first apparatus 400 has information “A-2” aslocation-related information or position-related information, andtransmits the information “A-2”.

At the position of a single circle 901-3 in FIG. 14, a first apparatushaving a configuration similar to that of the first apparatus 400 inFIG. 9 is installed. Hereinafter, the first apparatus having aconfiguration similar to that of the first apparatus 400 and installedat the position denoted by 901-3 will be referred to as a “third firstapparatus 400”. The third first apparatus 400 has information “A-3” aslocation-related information or position-related information, andtransmits the information “A-3”.

At the position of a single circle 901-4 in FIG. 14, a first apparatushaving a configuration similar to that of the first apparatus 400 inFIG. 9 is installed. Hereinafter, the first apparatus having aconfiguration similar to that of the first apparatus 400 and installedat the position denoted by 901-4 will be referred to as a “fourth firstapparatus 400”. The fourth first apparatus 400 has information “A-4” aslocation-related information or position-related information, andtransmits the information “A-4”.

At the position of a single circle 901-21 in FIG. 14, a first apparatushaving a configuration similar to that of the first apparatus 400 inFIG. 9 is installed. Hereinafter, the first apparatus having aconfiguration similar to that of the first apparatus 400 and installedat the position denoted by 901-21 will be referred to as a “twenty-firstfirst apparatus 400”. The twenty-first first apparatus 400 hasinformation “A-21” as location-related information or position-relatedinformation, and transmits the information “A-21”.

At the position of a single circle 901-22 in FIG. 14, a first apparatushaving a configuration similar to that of the first apparatus 400 inFIG. 9 is installed. Hereinafter, the first apparatus having aconfiguration similar to that of the first apparatus 400 and installedat the position denoted by 901-22 will be referred to as a“twenty-second first apparatus 400”. The twenty-second first apparatus400 has information “A-22” as location-related information orposition-related information, and transmits the information “A-22”.

At the position of a single circle 901-23 in FIG. 14, a first apparatushaving a configuration similar to that of the first apparatus 400 inFIG. 9 is installed. Hereinafter, the first apparatus having aconfiguration similar to that of the first apparatus 400 and installedat the position denoted by 901-23 will be referred to as a “twenty-thirdfirst apparatus 400”. The twenty-third first apparatus 400 hasinformation “A-23” as location-related information or position-relatedinformation, and transmits the information “A-23”.

At the position of a single circle 901-24 in FIG. 14, a first apparatushaving a configuration similar to that of the first apparatus 400 inFIG. 9 is installed. Hereinafter, the first apparatus having aconfiguration similar to that of the first apparatus 400 and installedat the position denoted by 901-24 will be referred to as a“twenty-fourth first apparatus 400”. The twenty-fourth first apparatus400 has information “A-24” as location-related information orposition-related information, and transmits the information “A-24”.

At the position of a double circle 902 in FIG. 14, a base station (orAP) having a configuration similar to that of the base station 470 inFIG. 9 is installed. Hereinafter, the base station (or AP) having aconfiguration similar to that of the base station 470 in FIG. 9 will besimply referred to as a “base station 470”. Here, it is assumed that theSSID of the base station 470 installed at the position denoted by 902 is“abcdef”.

The terminal 450 existing near the position indicated in the map in FIG.14 may access the base station 470 installed at the position denoted by902 in FIG. 14 when performing wireless communication.

Thus, the “first first apparatus 400” installed at 901-1 in FIG. 14transmits “abcdef” as SSID-related information (see 401-1 in FIG. 9).

Likewise, the “second first apparatus 400” installed at 901-2 in FIG. 14transmits “abcdef” as SSID-related information (see 401-1 in FIG. 9).

The “third first apparatus 400” installed at 901-3 in FIG. 14 transmits“abcdef” as SSID-related information (see 401-1 in FIG. 9).

The “fourth first apparatus 400” installed at 901-4 in FIG. 14 transmits“abcdef” as SSID-related information (see 401-1 in FIG. 9).

The “twenty-first first apparatus 400” installed at 901-21 in FIG. 14transmits “abcdef” as SSID-related information (see 401-1 in FIG. 9).

The “twenty-second first apparatus 400” installed at 901-22 in FIG. 14transmits “abcdef” as SSID-related information (see 401-1 in FIG. 9).

The “twenty-third first apparatus 400” installed at 901-23 in FIG. 14transmits “abcdef” as SSID-related information (see 401-1 in FIG. 9).

The “twenty-fourth first apparatus 400” installed at 901-24 in FIG. 14transmits “abcdef” as SSID-related information (see 401-1 in FIG. 9).

Hereinafter, a specific operation example will be described.

It is assumed that a terminal having a configuration similar to that ofthe terminal 450 in FIG. 9 (hereinafter simply referred to as a“terminal 450”) exists at the position denoted by 903-1 in FIG. 14. Inthis case, the terminal 450 receives a modulated signal transmitted bythe “fourth first apparatus 400” at the position denoted by 901-4 inFIG. 14 and obtains position information “A-4”. Also, the terminal 450receives a modulated signal transmitted by the “fourth first apparatus400” at the position denoted by 901-4 in FIG. 14 and obtains SSIDinformation “abcdef”. Accordingly, the terminal 450 accesses the basestation 470 positioned at 902 in FIG. 14. In addition, the terminal 450obtains information, such as a map, from the base station 470 positionedat 902 in FIG. 14. Subsequently, the terminal 450 displays the mapinformation and position information (see, for example, FIG. 10, whichmerely illustrates a display example).

Likewise, it is assumed that a terminal having a configuration similarto that of the terminal 450 in FIG. 9 (hereinafter simply referred to asa “terminal 450”) exists at the position denoted by 903-2 in FIG. 14. Inthis case, the terminal 450 receives a modulated signal transmitted bythe “twenty-second first apparatus 400” at the position denoted by901-22 in FIG. 14 and obtains position information “A-22”. Also, theterminal 450 receives a modulated signal transmitted by the “fourthfirst apparatus 400” at the position denoted by 901-22 in FIG. 14 andobtains SSID information “abcdef”. Accordingly, the terminal 450accesses the base station 470 positioned at 902 in FIG. 14. In addition,the terminal 450 obtains information, such as a map, from the basestation 470 positioned at 902 in FIG. 14. Subsequently, the terminal 450displays the map information and position information (see, for example,FIG. 10, which merely illustrates a display example).

The terminal 450 may record the map (neighborhood information) andposition information illustrated in FIG. 14 on a storage unit (notillustrated) included in the terminal 450 such that the informationrecorded on the storage unit can be retrieved when required by a userusing the terminal 450. Accordingly, the user is able to utilize the map(neighborhood information) and position information more conveniently.

As described above, the first apparatus 400 transmits a modulated signalby using visible light, and thus the terminal 450 capable of receivingthe modulated signal is limited to a terminal that is within the rangewhere the light signal can be received from the position of the firstapparatus 400. Thus, the terminal 450 is able to easily (withoutperforming complicated signal processing) obtain highly accurateposition information by receiving the location/position informationtransmitted by the first apparatus 400.

When the first apparatus 400 is installed at a location where a radiowave from a GPS satellite is difficult to receive, the terminal 450 isable to safely obtain highly accurate position information by receivinga modulated signal transmitted by the first apparatus 400 even in asituation where it is difficult to receive a radio wave from the GPSsatellite.

Furthermore, the terminal 450 is able to safely obtain information byestablishing a connection with the base station (or AP) 470 andobtaining information based on the SSID information transmitted by thefirst apparatus 400. This is because, when the terminal 450 obtainsinformation from a modulated signal of visible light, the user is ableto easily recognize the first apparatus 400 that has transmitted themodulated signal by visually perceiving it because the modulated signalis visible light, and also the user is able to easily determine whetherthe source of the information is safe. On the other hand, for example,when the SSID is obtained from a modulated signal of a radio wavetransmitted through a wireless LAN, it is difficult for the user todetermine the apparatus that has transmitted the radio wave. Therefore,visible light communication is more suitable for obtaining an SSID thanwireless LAN communication in terms of ensuring the safety ofinformation.

A plurality of signals may further be input to the radio device 453 ofthe terminal 450 in FIG. 9. For example, a control signal forcontrolling the radio device 453, information to be transmitted to thebase station 470, and so forth may be input to the radio device 453. Atthis time, the radio device 453 may start communication based on thecontrol signal, for example. As described above, in the presentembodiment, the configuration of the first apparatus is not limited tothe configuration of the first apparatus 400 in FIG. 9, theconfiguration of the terminal is not limited to the configuration of theterminal 450 in FIG. 9, and the connection destination and configurationof the base station are not limited to the connection destination andconfiguration of the base station 470 illustrated in FIG. 9.

FIG. 9 illustrates a case where there is a single base station 470, butthere may be a plurality of base stations (or APs) accessible to theterminal 450 (safe base stations). At this time, the SSID-related symboltransmitted by the first apparatus 400 in FIG. 9 may include informationindicating the SSIDs of the plurality of base stations (or APs). In thiscase, a list of the SSIDs of the plurality of base stations and/or alist of a plurality of access destinations is displayed on the display157 of the terminal 450 in FIG. 9, as an access destination displayoperation (the foregoing “first display operation”). Based on theinformation indicating the SSIDs of the plurality of base stations (orAPs), the terminal 450 in FIG. 9 may select one or more base stations tobe actually connected in a wireless manner (i.e., may simultaneouslyestablish connections with the plurality of base stations).

For example, it is assumed that there are three base stations 470. Here,the three base stations 470 are referred to as a base station #A, a basestation #B, and a base station #C. Also, it is assumed that the SSID ofthe base station #A is “abcdef”, the SSID of the base station #B is“ghijk”, and the SSID of the base station #C is “pqrstu”. In this case,the SSID-related symbol 600-1 in the frame configuration illustrated inFIG. 11 of the modulated signal transmitted by the first apparatus 400includes information indicating that “the SSID of the base station #A is‘abcdef’”, “the SSID of the base station #B is ‘ghijk’”, and “the SSIDof the base station #C is ‘pqrstu’”. The terminal 450 in FIG. 9 receivesthe SSID-related symbol 600-1 and selects one or more base stations 470to be actually connected in a wireless manner, based on the informationindicating that “the SSID of the base station #A is ‘abcdef’”, “the SSIDof the base station #B is ‘ghijk’”, and “the SSID of the base station #Cis ‘pqrstu’”.

Embodiment 4

FIG. 15 is a diagram illustrating an example of the configuration of acommunication system in the present embodiment.

The communication system in FIG. 15 includes, for example, an apparatus1000, a terminal 1050, and the base station (or AP) 470 thatcommunicates with the terminal 1050.

The apparatus 1000 includes, for example, a visible light source, alighting device, a light source, or a light (hereinafter referred to asthe light source 104), such as an LED. Hereinafter, the apparatus 1000may be referred to as a “second apparatus” in the present embodiment.

In the second apparatus 1000 illustrated in FIG. 15, the components thatoperate similarly to those of the first apparatus 100 illustrated inFIG. 6 are denoted by the same numerals. In the terminal 1050illustrated in FIG. 15, the components that operate similarly to thoseof the terminal 150 illustrated in FIG. 6 are denoted by the samenumerals. It is assumed that the communication between the radio device453 of the terminal 1050 and the base station 470 illustrated in FIG. 15is performed by using a radio wave, for example.

In the second apparatus 1000 in FIG. 15, the transmitter 102 receivesSSID-related information 1001-1, encryption-key-related information1001-2, and data 1002 as input, generates the (light) modulated signal103 based on these input signals, and outputs the modulated signal 103.The modulated signal 103 is transmitted, for example, from the lightsource 104.

Next, a description will be given of the SSID-related information 1001-1and the encryption-key-related information 1001-2.

First, a description will be given of the SSID-related information1001-1.

The SSID-related information 1001-1 is information indicating the SSIDof the base station 470 in FIG. 15. For example, the base station 470transmits a modulated signal to the terminal 1050 by using a radio waveand receives a modulated signal from the terminal 1050 by using a radiowave. That is, the second apparatus 1000 is able to provide the terminal1050 with access to the base station 470, which is a safe accessdestination. Accordingly, the terminal 1050 in FIG. 15 is able to safelyobtain information from the base station 470.

On the other hand, the second apparatus 1000 is able to limit theterminal that accesses the base station 470 to a terminal positioned ina space where a light signal transmitted (emitted) by the secondapparatus 1000 can be received.

When the terminal 1050 receives a light signal transmitted in apredetermined scheme, the terminal 1050 may determine that the notifiedSSID is the SSID of a safe base station. The terminal 1050 mayseparately perform a process of determining whether or not the notifiedSSID is safe. For example, the second apparatus 1000 may transmit alight signal including a predetermined identifier, and the terminal 1050may determine, based on the received identifier, whether or not thenotified SSID is the SSID of a safe base station.

FIG. 15 illustrates a single base station 470. For example, also when abase station (or AP) other than the base station 470 exists, theterminal 1050 accesses the base station 470 by using the SSID obtainedfrom the second apparatus 1000 and obtains information.

Next, a description will be given of the encryption-key-relatedinformation 1001-2.

The encryption-key-related information 1001-2 is information about anencryption key that is necessary for the terminal 1050 to communicatewith the base station 470. The terminal 1050 obtains theencryption-key-related information 1001-2 from the second apparatus1000, thereby becoming able to perform encrypted communication with thebase station 470.

The SSID-related information 1001-1 and the encryption-key-relatedinformation 1001-2 have been described above.

The terminal 1050 in FIG. 15 receives a modulated signal transmitted bythe second apparatus 1000. In the terminal 1050 in FIG. 15, thecomponents that operate similarly to those of the terminal 150 in FIG. 6or those of the terminal 450 in FIG. 9 are denoted by the same numerals.

The light receiver 151 included in the terminal 1050 is, for example, animage sensor, such as a CMOS sensor or an organic CMOS sensor. The lightreceiver 151 receives light including the modulated signal transmittedby the second apparatus 1000 and outputs the reception signal 152.

The receiver 153 receives the reception signal 152 received by the lightreceiver 151 as input, performs processing, such as demodulation anderror-correction decoding, on the modulated signal included in thereception signal 152, and outputs the reception data 154.

The data analyzer 155 receives the reception data 154 as input andoutputs, for example, SSID information 1051 on a base station as aconnection destination and encryption key information 1052 forcommunicating with the base station as the connection destination, whichare included in the reception data 154. For example, in a wireless localarea network (LAN), Wired Equivalent Privacy (WEP), Wi-Fi ProtectedAccess (WPA), and Wi-Fi Protected Access 2 (WPA2) (Pre-Shared Key (PSK)mode, Extended Authentication Protocol (EAP) mode) are available as anencryption scheme. Note that the encryption scheme is not limitedthereto.

The display 157 receives the SSID information 1051 and the encryptionkey information 1052 as input, and displays, for example, the SSID andthe encryption key of a communication partner that the radio device 453included in the terminal 1050 is to access (this display operation isreferred to as a “first display operation” in the present embodiment).

For example, after the first display operation, the radio device 453receives the SSID information 1051 and the encryption key information1052 as input, and establishes a connection with the base station 470(for example, a radio wave is used for the connection). At this time,when the base station 470 communicates with the radio device 453included in the terminal 1050, the base station 470 transmits amodulated signal by using a radio wave, for example.

After that, the radio device 453 receives data 1053 and a control signal1054 as input, modulates the data 1053 in accordance with controlindicated by the control signal 1054, and transmits a modulated signalby using a radio wave.

Subsequently, for example, the base station 470 performs datatransmission (471) by using a network and data reception (472) by usingthe network. After that, for example, the base station 470 transmits amodulated signal to the terminal 1050 by using a radio wave.

The radio device 453 included in the terminal 1050 performs processing,such as demodulation and error-correction decoding, on the modulatedsignal received by using a radio wave, and obtains reception data 1056.The display 157 performs display based on the reception data 1056.

FIG. 16 illustrates an example of the frame configuration of themodulated signal transmitted by the second apparatus 1000 illustrated inFIG. 15. In FIG. 16, the horizontal axis indicates time. In FIG. 16, thesymbols similar to those in FIG. 7 or 11 are denoted by the samenumerals, and the description thereof is omitted.

The SSID-related symbol 600-1 is a symbol for transmitting theSSID-related information 1001-1 in FIG. 15, and a encryption-key-relatedsymbol 1101 is a symbol for transmitting the encryption-key-relatedinformation 1001-2 in FIG. 15. A data symbol 1102 is a symbol fortransmitting the data 1002 in FIG. 15.

The second apparatus 1000 transmits the preamble 201, the controlinformation symbol 202, the SSID-related symbol 600-1, theencryption-key-related symbol 1101, and the data symbol 1102. The secondapparatus 1000 may transmit a frame including a symbol other than thesymbols illustrated in FIG. 16. The frame configuration, including theorder in which the symbols are transmitted, is not limited to theconfiguration in FIG. 16.

FIG. 17 illustrates an example of the frame configuration of themodulated signal transmitted by the radio device 453 included in theterminal 1050 in FIG. 15. In FIG. 17, the horizontal axis indicatestime.

As illustrated in FIG. 17, the radio device 453 included in the terminal1050 transmits, for example, a preamble 1201, and then transmits acontrol information symbol 1202 and an information symbol 1203.

The preamble 1201 is a symbol by which the base station 470 thatreceives the modulated signal transmitted by radio device 453 of theterminal 1050 performs, for example, signal detection, timesynchronization, frame synchronization, frequency synchronization,frequency offset estimation, and the like.

The control information symbol 1202 is a symbol including, for example,data of information about an error-correction coding scheme and amodulation scheme that are used to generate the modulated signal,information about the frame configuration, and information about atransmission method. The base station 470 performs demodulation or thelike on the modulated signal based on the information included in thecontrol information symbol 1202.

The information symbol 1203 is a symbol by which the radio device 453 ofthe terminal 1050 transmits data.

The radio device 453 of the terminal 1050 may transmit a frame includinga symbol other than the symbols illustrated in FIG. 17. For example, theradio device 453 may transmit a frame in which a pilot symbol (referencesymbol) is included in a middle of the information symbol 1203. Theframe configuration, including the order in which the symbols aretransmitted, is not limited to the configuration in FIG. 17. In FIG. 17,a plurality of symbols may exist in the frequency axis direction. Thatis, symbols may exist at a plurality of frequencies (a plurality ofcarriers) in FIG. 17. In addition, in Embodiment 3, the frameconfiguration in FIG. 17 may be used when the radio device 453 includedin the terminal 450 in FIG. 9 transmits a modulated signal.

The frame configuration of the modulated signal transmitted by the basestation 470 in the present embodiment is similar to the frameconfiguration in FIG. 12 described in Embodiment 3. That is, asillustrated in FIG. 12, the base station 470 transmits, for example, thepreamble 701, and then transmits the control information symbol 702 andthe information symbol 703.

The preamble 701 is a symbol by which the radio device 453 of theterminal 1050 that receives the modulated signal transmitted by the basestation 470 performs, for example, signal detection, timesynchronization, frame synchronization, frequency synchronization,frequency offset estimation, and the like.

The control information symbol 702 is a symbol including, for example,data of information about an error-correction coding scheme and amodulation scheme that are used to generate the modulated signal,information about the frame configuration, and information about atransmission method. The radio device 453 of the terminal 1050 performsdemodulation or the like on the modulated signal based on theinformation of the control information symbol 702.

The information symbol 703 is a symbol by which the base station 470transmits data.

The base station 470 illustrated in FIG. 15 may transmit a frameincluding a symbol other than the symbols illustrated in FIG. 12. Forexample, the base station 470 may transmit a frame in which a pilotsymbol (reference symbol) is included in a middle of the informationsymbol 703. The frame configuration, including the order in which thesymbols are transmitted, is not limited to the configuration in FIG. 12.In FIG. 12, a plurality of symbols may exist in the frequency axisdirection. That is, symbols may exist at a plurality of frequencies (aplurality of carriers) in FIG. 12.

In addition, for example, the modulated signal that is transmitted bythe second apparatus 1000 and that has the frame configuration in FIG.16 may be repeatedly transmitted at a regular interval, for example.Accordingly, a plurality of terminals 1050 are able to perform theabove-described operation.

FIG. 18 is a flowchart illustrating an example of a process performed bythe “second apparatus 1000”, the “terminal 1050”, and the “base station470” illustrated in FIG. 15.

First, the second apparatus 1000 transmits a modulated signal having theframe configuration illustrated in FIG. 16 (ST1301).

Subsequently, the terminal 1050 receives the modulated signaltransmitted by the second apparatus 1000 and obtains the SSID of thebase station 470 that the terminal 1050 is to access (ST1302).

Also, the terminal 1050 obtains an encryption key to be used forcommunication with the base station 470 that the terminal 1050 is toaccess (ST1303).

Subsequently, the terminal 1050 establishes a connection through a radiowave with the base station 470 (ST1304). The establishment of theconnection with the base station 470 is completed upon receipt of aresponse from the base station 470 by the terminal 1050 (ST1305).

Subsequently, the terminal 1050 transmits information on the connectiondestination to the base station 470 by using a radio wave (ST1306).

The base station 470 obtains information to be transmitted to theterminal 1050 from the network (ST1307).

Subsequently, the base station 470 transmits the obtained information tothe terminal 1050 by using a radio wave, and the terminal 1050 obtainsthe information (ST1308). The terminal 1050 obtains necessaryinformation from the network via the base station 470 when necessary,for example.

As described above, based on the SSID information and the encryption keyinformation transmitted by the second apparatus 1000, the terminal 1050establishes a connection with the base station 470 and obtainsinformation, thereby being able to safely obtain the information via thebase station 470 that is safety-guaranteed. This is because, when theterminal 1050 obtains information from a modulated signal of visiblelight, the user is able to easily determine whether or not the source ofthe information is safe because modulated signal is visible light. Incontrast, for example, when the SSID is obtained from a modulated signalof a radio wave transmitted through a wireless LAN, it is difficult forthe user to determine the apparatus that has transmitted the radio wave.Therefore, visible light communication is more suitable for obtainingthe SSID than wireless LAN communication in terms of ensuring the safetyof information.

In the present embodiment, a description has been given of a case wherethe second apparatus 1000 transmits encryption key information. However,when the base station 470 does not perform encrypted communication usingan encryption key, for example, it is sufficient that the secondapparatus 1000 transmit only SSID-related information, not encryptionkey information. In this case, a similar operation can be performed onlyby removing the component related to the encryption key among theabove-described components.

The configuration of the second apparatus is not limited to theconfiguration of the second apparatus 1000 illustrated in FIG. 15, theconfiguration of the terminal is not limited to the configuration of theterminal 1050 illustrated in FIG. 15, and the connection destination andthe configuration of the base station are not limited to the connectiondestination and the configuration of the base station 470 illustrated inFIG. 15.

FIG. 15 illustrates a case where there is a single base station 470, butthere may be a plurality of base stations (or APs) accessible to theterminal 1050 (safe base stations). The plurality of base stations andthe terminal 1050 each transmit/receive a modulated signal by using aradio wave. At this time, the SSID-related symbol transmitted by thesecond apparatus 1000 in FIG. 15 may include information indicating theSSIDs of the plurality of base stations (or APs). In this case, a listof the SSIDs of the plurality of base stations and/or a list of aplurality of access destinations is displayed on the display 157 of theterminal 1050 in FIG. 15, as an access destination display operation.The encryption-key-related symbol transmitted by the second apparatus1000 in FIG. 15 may include information indicating the encryption keysthat are used to connect to the plurality of base stations (or APs).Based on the information indicating the SSIDs and encryption keys of theplurality of base stations, the terminal 1050 in FIG. 15 may select oneor more base stations to be actually connected in a wireless manner (forexample, by using a radio wave) (i.e., may simultaneously establishconnections with the plurality of base stations).

For example, it is assumed that there are three base stations 470. Here,the three base stations 470 are referred to as a base station #A, a basestation #B, and a base station #C. Also, it is assumed that the SSID ofthe base station #A is “abcdef”, the SSID of the base station #B is“ghijk”, and the SSID of the base station #C is “pqrstu”. Also, it isassumed that the encryption key for connecting to the base station #A is“123”, the encryption key for connecting to the base station #B is“456”, and the encryption key for connecting to the base station #C is“789”.

In this case, the SSID-related symbol 600-1 in the frame configurationillustrated in FIG. 16 of the modulated signal transmitted by the secondapparatus 1000 includes information indicating that “the SSID of thebase station #A is ‘abcdef’”, “the SSID of the base station #B is‘ghijk’”, and “the SSID of the base station #C is ‘pqrstu’”. Theencryption-key-related symbol 1101 in the frame configuration in FIG. 16includes information indicating that “the encryption key for connectingto the base station #A is ‘123’”, “the encryption key for connecting tothe base station #B is ‘456’”, and “the encryption key for connecting tothe base station #C is ‘789’”.

The terminal 1050 in FIG. 15 receives the SSID-related symbol 600-1 andobtains the information indicating that “the SSID of the base station #Ais ‘abcdef’”, “the SSID of the base station #B is ‘ghijk’”, and “theSSID of the base station #C is ‘pqrstu’”. Also, the terminal 1050receives the encryption-key-related symbol 1101 and obtains theinformation indicating that “the encryption key for connecting to thebase station #A is ‘123’”, “the encryption key for connecting to thebase station #B is ‘456’”, and “the encryption key for connecting to thebase station #C is ‘789’”. Based on these pieces of information, theterminal 1050 selects one or more base stations to be actually connectedin a wireless manner (for example, by using a radio wave), andestablishes the connection.

As in the present embodiment, with the base station 470 to be accessedby the terminal 1050 being set by using a light source, such as an LED,it becomes unnecessary to provide a mode for a special setting forperforming a procedure for connection through wireless communicationbetween the terminal 1050 and the base station 470 on a modulated signalfor wireless communication transmitted by the terminal 1050. Also, itbecomes unnecessary to provide a mode for a special setting forperforming a procedure for connection through wireless communicationbetween the terminal 1050 and the base station 470 on a modulated signaltransmitted by the base station 470. Accordingly, in the presentembodiment, the data transmission efficiency of wireless communicationcan be increased.

As described above, the encryption key may be an encryption key for anSSID of a wireless LAN, or may be an encryption key for limiting aconnection style, a service style, a connection range of a network, orthe like. That is, it is sufficient that an encryption key be introducedto limit something.

Embodiment 5

FIG. 19 is a diagram illustrating an example of the configuration of acommunication system in the present embodiment.

The communication system in FIG. 19 includes, for example, apparatuses1400A and 1400B, the terminal 1050, and the base station (or AP) 470that communicates with the terminal 1050.

The apparatuses 1400A and 1400B each include, for example, a visiblelight source, a lighting device, a light source, or a light (hereinafterreferred to as light sources 1406-1 and 1406-2), such as an LED.Hereinafter, the apparatus 1400A will be referred to as a “thirdapparatus” in the present embodiment, and the apparatus 1400B will bereferred to as a “fourth apparatus” in the present embodiment.

In the terminal 1050 illustrated in FIG. 19, the components that operatesimilarly to those of the terminal 150 illustrated in FIG. 6 or theterminal 1050 illustrated in FIG. 15 are denoted by the same numerals.In the base station (or AP) 470 illustrated in FIG. 19, the componentsthat operate similarly to those of the base station 470 illustrated inFIG. 9 are denoted by the same numerals as in FIG. 9. It is assumed thatthe communication between the radio device 453 of the terminal 1050 andthe base station 470 illustrated in FIG. 19 is performed by using aradio wave, for example.

In the third apparatus 1400A in FIG. 19, a transmitter 1404-1 receivesSSID-related information 1401-1 and data 1402-1 as input, generates a(light) modulated signal 1405-1 based on these input signals, andoutputs the modulated signal 1405-1. The modulated signal 1405-1 istransmitted, for example, from the light source 1406-1.

In the fourth apparatus 1400B in FIG. 19, a transmitter 1404-2 receivesencryption-key-related information 1403-2 and data 1402-2 as input,generates a (light) modulated signal 1405-2 based on these inputsignals, and outputs the modulated signal 1405-2. The modulated signal1405-2 is transmitted, for example, from the light source 1406-2.

Next, a description will be given of the SSID-related information 1401-1and the encryption-key-related information 1403-2.

First, a description will be given of the SSID-related information1401-1.

The SSID-related information 1401-1 is information indicating the SSIDof the base station 470 in FIG. 19. That is, the third apparatus 1400Ais able to provide the terminal 1050 with access to the base station470, which is a safe access destination using a radio wave. Accordingly,the terminal 1050 in FIG. 19 is able to safely obtain information fromthe base station 470.

When the terminal 1050 receives a light signal transmitted in apredetermined scheme, the terminal 1050 may determine that the notifiedSSID is the SSID of a safe base station. The terminal 1050 mayseparately perform a process of determining whether or not the notifiedSSID is safe. For example, the third apparatus 1400A may transmit alight signal including a predetermined identifier, and the terminal 1050may determine, based on the received identifier, whether or not thenotified SSID is the SSID of a safe base station.

FIG. 19 illustrates a single base station 470. For example, also when abase station (or AP) other than the base station 470 exists, theterminal 1050 accesses the base station 470 by using the SSID obtainedfrom the third apparatus 1400A and the encryption key obtained from thefourth apparatus 1400B and obtains information.

Next, a description will be given of the encryption-key-relatedinformation 1403-2.

The encryption-key-related information 1403-2 is information about anencryption key that is necessary for the terminal 1050 to communicatewith the base station 470 by using a radio wave. The terminal 1050obtains the encryption-key-related information 1403-2 from the fourthapparatus 1400B, thereby becoming able to perform encryptedcommunication with the base station 470.

The SSID-related information 1401-1 and the encryption-key-relatedinformation 1403-2 have been described above.

The terminal 1050 in FIG. 19 receives a modulated signal transmitted bythe third apparatus 1400A.

The light receiver 151 included in the terminal 1050 is, for example, animage sensor, such as a CMOS sensor or an organic CMOS sensor. The lightreceiver 151 receives light including the modulated signal transmittedby the third apparatus 1400A and outputs the reception signal 152.

The receiver 153 receives the reception signal 152 received by the lightreceiver 151 as input, performs processing, such as demodulation anderror-correction decoding, on the modulated signal included in thereception signal 152, and outputs the reception data 154.

The data analyzer 155 receives the reception data 154 as input andoutputs, for example, the SSID information 1051 on a base station as aconnection destination, which is included in the reception data. Theradio device 453 obtains, from the SSID information 1051, the SSIDinformation on the base station 470 to be connected to the radio device453 by using a radio wave.

The terminal 1050 in FIG. 19 receives a modulated signal transmitted bythe fourth apparatus 1400B.

The light receiver 151 included in the terminal 1050 is, for example, animage sensor, such as a CMOS sensor or an organic CMOS sensor. The lightreceiver 151 receives light including the modulated signal transmittedby the fourth apparatus 1400B and outputs the reception signal 152.

The receiver 153 receives the reception signal 152 received by the lightreceiver 151 as input, performs processing, such as demodulation anderror-correction decoding, on the modulated signal included in thereception signal 152, and outputs the reception data 154.

The data analyzer 155 receives the reception data 154 as input andoutputs, for example, the encryption key information 1052 forcommunicating with the base station as a connection destination, whichis included in the reception data. For example, in a wireless local areanetwork (LAN), Wired Equivalent Privacy (WEP), Wi-Fi Protected Access(WPA), and Wi-Fi Protected Access 2 (WPA2) (Pre-Shared Key (PSK) mode,Extended Authentication Protocol (EAP) mode) are available as anencryption scheme. Note that the encryption scheme is not limitedthereto.

The radio device 453 included in the terminal 1050 obtains, from theencryption key information 1052 for communicating with the base stationas the connection destination (for example, through a radio wave), theencryption key information on the base station 470 to be connected tothe radio device 453.

The display 157 receives the SSID information 1051 and the encryptionkey information 1052 as input, and displays, for example, the SSID andthe encryption key of a communication partner that the radio device 453included in the terminal 1050 is to access (this display operation isreferred to as a “first display operation” in the present embodiment).

For example, after the first display operation, the radio device 453receives the SSID information 1051 and the encryption key information1052 as input, and establishes a connection through a radio wave withthe base station 470. At this time, when the base station 470communicates with the radio device 453 included in the terminal 1050,the base station 470 transmits a modulated signal by using a radio wave,for example.

After that, the radio device 453 receives the data 1053 and the controlsignal 1054 as input, modulates the data 1053 in accordance with controlindicated by the control signal 1054, and transmits a modulated signalby using a radio wave.

Subsequently, for example, the base station 470 performs datatransmission (471) by using a network and data reception (472) by usingthe network. After that, for example, the base station 470 transmits amodulated signal to the terminal 1050 by using a radio wave.

The radio device 453 included in the terminal 1050 performs processing,such as demodulation and error-correction decoding, on the modulatedsignal received by using a radio wave, and obtains the reception data1056. The display 157 performs display based on the reception data 1056.

FIG. 20 illustrates an example of the frame configuration of themodulated signal transmitted by the third apparatus 1400A illustrated inFIG. 19. In FIG. 20, the horizontal axis indicates time. In FIG. 20, thesymbols similar to those in FIG. 7, 11 or 16 are denoted by the samenumerals, and the description thereof is omitted.

The SSID-related symbol 600-1 is a symbol for transmitting theSSID-related information 1401-1 in FIG. 19. The data symbol 1102 is asymbol for transmitting the data 1402-1.

The third apparatus 1400A transmits the preamble 201, the controlinformation symbol 202, the SSID-related symbol 600-1, and the datasymbol 1102. The third apparatus 1400A may transmit a frame including asymbol other than the symbols illustrated in FIG. 20. The frameconfiguration, including the order in which the symbols are transmitted,is not limited to the configuration in FIG. 20.

FIG. 21 illustrates an example of the frame configuration of themodulated signal transmitted by the fourth apparatus 1400B illustratedin FIG. 19. In FIG. 21, the horizontal axis indicates time. In FIG. 21,the symbols similar to those in FIG. 7 or 16 are denoted by the samenumerals, and the description thereof is omitted.

The encryption-key-related symbol 1101 is a symbol for transmitting theencryption-key-related information 1403-2 in FIG. 19. The data symbol1102 is a symbol for transmitting the data 1402-2.

The fourth apparatus 1400B transmits the preamble 201, the controlinformation symbol 202, the encryption-key-related symbol 1101, and thedata symbol 1102. The fourth apparatus 1400B in FIG. 19 may transmit aframe including a symbol other than the symbols illustrated in FIG. 21.The frame configuration, including the order in which the symbols aretransmitted, is not limited to the configuration in FIG. 21.

The frame configuration of the modulated signal transmitted by the radiodevice 453 in the present embodiment is similar to the frameconfiguration in FIG. 17 described in Embodiment 4. That is, asillustrated in FIG. 17, the radio device 453 included in the terminal1050 transmits, for example, the preamble 1201, and then transmits thecontrol information symbol 1202 and the information symbol 1203.

The preamble 1201 is a symbol by which the base station (or AP) 470 thatreceives the modulated signal transmitted by radio device 453 of theterminal 1050 in FIG. 19 performs, for example, signal detection, timesynchronization, frame synchronization, frequency synchronization,frequency offset estimation, and the like.

The control information symbol 1202 is a symbol including, for example,data of information about an error-correction coding scheme and amodulation scheme that are used to generate the modulated signal,information about the frame configuration, and information about atransmission method. The base station 470 performs demodulation or thelike on the modulated signal based on the information included in thecontrol information symbol 1202.

The information symbol 1203 is a symbol by which the radio device 453 ofthe terminal 1050 transmits data.

The radio device 453 of the terminal 1050 illustrated in FIG. 19 maytransmit a frame including a symbol other than the symbols illustratedin FIG. 17. For example, the radio device 453 may transmit a frame inwhich a pilot symbol (reference symbol) is included in a middle of theinformation symbol 1203. The frame configuration, including the order inwhich the symbols are transmitted, is not limited to the configurationin FIG. 17. In FIG. 17, a plurality of symbols may exist in thefrequency axis direction. That is, symbols may exist at a plurality offrequencies (a plurality of carriers) in FIG. 17.

The frame configuration of the modulated signal transmitted by the basestation 470 in the present embodiment is similar to the frameconfiguration in FIG. 12 described in Embodiment 3. That is, asillustrated in FIG. 12, the base station 470 transmits, for example, thepreamble 701, and then transmits the control information symbol 702 andthe information symbol 703.

The preamble 701 is a symbol by which the radio device 453 of theterminal 1050 in FIG. 19 that receives the modulated signal transmittedby the base station 470 performs, for example, signal detection, timesynchronization, frame synchronization, frequency synchronization,frequency offset estimation, and the like.

The control information symbol 702 is a symbol including, for example,data of information about an error-correction coding scheme and amodulation scheme that are used to generate the modulated signal,information about the frame configuration, and information about atransmission method. The radio device 453 of the terminal 1050 in FIG.19 performs demodulation or the like on the modulated signal based onthe information of the control information symbol 702.

The information symbol 703 is a symbol by which the base station 470 inFIG. 19 transmits data.

The base station 470 illustrated in FIG. 19 may transmit a frameincluding a symbol other than the symbols illustrated in FIG. 12. Forexample, the base station 470 may transmit a frame in which a pilotsymbol (reference symbol) is included in a middle of the informationsymbol 703. The frame configuration, including the order in which thesymbols are transmitted, is not limited to the configuration in FIG. 12.In FIG. 12, a plurality of symbols may exist in the frequency axisdirection. That is, symbols may exist at a plurality of frequencies (aplurality of carriers) in FIG. 12.

In addition, for example, the modulated signal that is transmitted bythe third apparatus 1400A and that has the frame configuration in FIG.20 may be repeatedly transmitted at a regular interval, for example.Accordingly, a plurality of terminals 1050 are able to perform theabove-described operation. Likewise, the modulated signal that istransmitted by the fourth apparatus 1400B and that has the frameconfiguration in FIG. 21 may be repeatedly transmitted at a regularinterval, for example. Accordingly, a plurality of terminals 1050 areable to perform the above-described operation.

FIG. 22 is a flowchart illustrating a first example of a processperformed by the “third apparatus 1400A”, the “fourth apparatus 1400B”,the “terminal 1050”, and the “base station 470” illustrated in FIG. 19.In FIG. 22, the steps similar to those in FIG. 18 are denoted by thesame numerals.

First, the third apparatus 1400A transmits a modulated signal having theframe configuration illustrated in FIG. 20 (ST1701).

Subsequently, the terminal 1050 receives the modulated signaltransmitted by the third apparatus 1400A and obtains the SSID of thebase station 470 that the terminal 1050 is to access (ST1702).

Subsequently, the fourth apparatus 1400B transmits a modulated signalhaving the frame configuration illustrated in FIG. 21 (ST1703).

Subsequently, the terminal 1050 receives the modulated signaltransmitted by the fourth apparatus 14006 and obtains the encryption keyto be used for the communication with the base station 470 that theterminal 1050 is to access (ST1704).

Subsequently, the terminal 1050 establishes a connection through a radiowave with the base station 470 (ST1304). The establishment of theconnection through a radio wave with the base station 470 is completedupon receipt of a response from the base station 470 by the terminal1050 (ST1305).

Subsequently, the terminal 1050 transmits information on the connectiondestination to the base station 470 by using a radio wave (ST1306).

The base station 470 obtains information to be transmitted to theterminal 1050 from the network (ST1307).

Subsequently, the base station 470 transmits the obtained information tothe terminal 1050 by using a radio wave, and the terminal 1050 obtainsthe information (ST1308). The terminal 1050 obtains necessaryinformation from the network via the base station 470 when necessary,for example.

FIG. 23 is a flowchart illustrating a second example of a processperformed by the “third apparatus 1400A”, the “fourth apparatus 1400B”,the “terminal 1050”, and the “base station 470” illustrated in FIG. 19.In FIG. 23, the steps similar to those in FIG. 18 are denoted by thesame numerals.

First, the fourth apparatus 1400B transmits a modulated signal havingthe frame configuration illustrated in FIG. 21 (ST1801).

Subsequently, the terminal 1050 receives the modulated signaltransmitted by the fourth apparatus 14006 and obtains the encryption keyto be used for the communication with the base station 470 that theterminal 1050 is to access (ST1802).

Subsequently, the third apparatus 1400A transmits a modulated signalhaving the frame configuration illustrated in FIG. 20 (ST1803).

Subsequently, the terminal 1050 receives the modulated signaltransmitted by the third apparatus 1400A and obtains the SSID of thebase station 470 that the terminal 1050 is to access (ST1804).

Subsequently, the terminal 1050 establishes a connection through a radiowave with the base station 470 (ST1304). The establishment of theconnection through a radio wave with the base station 470 is completedupon receipt of a response from the base station 470 by the terminal1050 (ST1305).

Subsequently, the terminal 1050 transmits information on the connectiondestination to the base station 470 by using a radio wave (ST1306).

The base station 470 obtains information to be transmitted to theterminal 1050 from the network (ST1307).

Subsequently, the base station 470 transmits the obtained information tothe terminal 1050 by using a radio wave, and the terminal 1050 obtainsthe information (ST1308). The terminal 1050 obtains necessaryinformation from the network via the base station 470 when necessary,for example.

As described above, based on the SSID transmitted by the third apparatus1400A and the encryption key information transmitted by the fourthapparatus 1400B, the terminal 1050 establishes a connection with thebase station 470 and obtains information. That is, the apparatus fromwhich the terminal 1050 obtains SSID information is different from theapparatus from which the terminal 1050 obtains encryption keyinformation, and thus information can be safely obtained via the basestation 470 that is safety-guaranteed. This is because, when theterminal 1050 obtains information from a modulated signal of visiblelight, the user is able to easily determine whether or not the source ofthe information is safe because modulated signal is visible light. Incontrast, for example, when the SSID is obtained from a modulated signalof a radio wave transmitted through a wireless LAN, it is difficult forthe user to determine the apparatus that has transmitted the radio wave.Therefore, visible light communication is more suitable for obtainingthe SSID than wireless LAN communication in terms of ensuring the safetyof information.

In the present embodiment, a description has been given of a case wherethe fourth apparatus 1400B transmits encryption key information.However, for example, when the base station 470 does not performencrypted communication using an encryption key, it is sufficient thatthe third apparatus 1400A transmit only SSID-related information, andthe fourth apparatus 1400B does not need to transmit cryptographic keyinformation. In this case, a similar operation can be performed only byremoving the component related to the encryption key among theabove-described components.

As in the present embodiment, when the apparatus that transmitsSSID-related information (the third apparatus 1400A) and the apparatusthat transmits encryption-key-related information (the fourth apparatus14006) are different from each other, the terminal 1050 is able tocommunicate with the base station 470 more safely.

For example, it is assumed that there is a space illustrated in FIG. 24.In FIG. 24, there are an area #1 and an area #2, and there is anentrance/exit and a wall between the area #1 and the area #2. That is,in the space in FIG. 24, a movement from the area #1 to the area #2, anda movement from the area #2 to the area #1 is possible only through theentrance/exit.

It is assumed that the base station 470, the third apparatus 1400A, andthe fourth apparatus 1400B are installed in the area #1 in FIG. 24. Onthe other hand, it is assumed that only the third apparatus 1400A isinstalled in the area #2. In addition, it is assumed that, in FIG. 24,the radio wave transmitted by the base station 470 can be received ineach of the area #1 and the area #2.

At this time, the terminal 1050 existing in the area #1 where the fourthapparatus 1400B is installed becomes able to communicate with the basestation 470 by obtaining the encryption key of the base station 470 fromthe fourth apparatus 1400B. If the terminal 1050 that has established aconnection with the base station 470 in the area #1 moves to the area#2, the terminal 1050 is able to communicate with the base station 470by using an encryption key that has been obtained from the fourthapparatus 1400B in the area #1. If the terminal 1050 that hasestablished a connection with the base station 470 in the area #1 movesto an area other than the area #1 and the area #2 and then returns toeither the area #1 or the area #2, the terminal 1050 is able tocommunicate with the base station 470 by using the encryption key thathas been obtained from the fourth apparatus 1400B in the area #1.

On the other hand, the terminal 1050 that is not able to enter the area#1 is not able to obtain an encryption key from the fourth apparatus1400B. In this case, the terminal 1050 has only the SSID of the basestation (or AP) 470. In this case, for example, the terminal 1050 may beallowed to communicate with the base station 470 by using a service thatis available when having only the SSID of the base station 470. Theservice that is available when having only the SSID of the base station470 may be more limited than a service that is available when havingboth the SSID and the encryption key.

Thus, only the terminal 1050 that has been able to enter the area #1 isable to communicate with the base station 470. Accordingly, the safetyin communication can be ensured. In addition, it becomes possible toestablish a system in which a different service can be provided in eacharea.

If the terminal 1050 changes the encryption key for communicating withthe base station 470 (for example, in each time section), the terminal1050 holding an encryption key before change is not able to communicatewith the base station 470. With such an operation, communication can beperformed more safely.

The configuration of the third apparatus and the configuration of thefourth apparatus are not limited to the configuration of the thirdapparatus 1400A and the configuration of the fourth apparatus 1400Billustrated in FIG. 19, respectively. The configuration of the terminalis not limited to the configuration of the terminal 1050 illustrated inFIG. 19. The connection destination and the configuration of the basestation are not limited to the connection destination and theconfiguration of the base station 470 illustrated in FIG. 19.

FIG. 19 illustrates a case where there is a single base station 470, butthere may be a plurality of base stations (or APs) accessible to theterminal 1050 (safe base stations). At this time, the SSID-relatedsymbol transmitted by the third apparatus 1400A in FIG. 19 may includeinformation indicating the SSIDs of the plurality of base stations 470.The encryption-key-related symbol transmitted by the fourth apparatus1400B in FIG. 19 may include information about encryption keys to beused to connect to the plurality of base stations. In this case, a listof the SSIDs of the plurality of base stations and/or a list of aplurality of access destinations is displayed on the display 157 of theterminal 1050 in FIG. 19, as an access destination display operation(the above-described “first display operation”). Based on theinformation on the SSIDs and encryption keys of the plurality of basestations, the terminal 1050 in FIG. 19 may select one or more basestations to be actually connected in a wireless manner (i.e., maysimultaneously establish connections with the plurality of basestations).

For example, it is assumed that there are three base stations 470. Here,the three base stations 470 are referred to as a base station #A, a basestation #B, and a base station #C. Also, it is assumed that the SSID ofthe base station #A is “abcdef”, the SSID of the base station #B is“ghijk”, and the SSID of the base station #C is “pqrstu”. Also, it isassumed that the encryption key for connecting to the base station #A is“123”, the encryption key for connecting to the base station #B is“456”, and the encryption key for connecting to the base station #C is“789”.

In this case, the SSID-related symbol 600-1 in the frame configurationin FIG. 20 of the modulated signal transmitted by the third apparatus1400A includes information indicating that “the SSID of the base station#A is ‘abcdef’”, “the SSID of the base station #B is ‘ghijk’”, and “theSSID of the base station #C is ‘pqrstu’”. The encryption-key-relatedsymbol 1101 in the frame configuration in FIG. 21 of the modulatedsignal transmitted by the fourth apparatus 1400B includes informationindicating that “the encryption key for connecting to the base station#A is ‘123’”, “the encryption key for connecting to the base station #Bis ‘456’”, and “the encryption key for connecting to the base station #Cis ‘789’”.

The terminal 1050 in FIG. 19 receives the SSID-related symbol 600-1 andobtains the information indicating that “the SSID of the base station #Ais ‘abcdef’”, “the SSID of the base station #B is ‘ghijk’”, and “theSSID of the base station #C is ‘pqrstu’”. Also, the terminal 1050receives the encryption-key-related symbol 1101 and obtains theinformation indicating that “the encryption key for connecting to thebase station #A is ‘123’”, “the encryption key for connecting to thebase station #B is ‘456’”, and “the encryption key for connecting to thebase station #C is ‘789’”. Based on these pieces of information, theterminal 1050 selects a base station to be connected in a wirelessmanner (for example, by using a radio wave), and establishes theconnection.

As in the present embodiment, with the base station 470 to be accessedby the terminal 1050 being set by using a light source, such as an LED,it becomes unnecessary to provide a mode for a special setting forperforming a procedure for connection through wireless communicationbetween the terminal 1050 and the base station 470 on a modulated signalfor wireless communication transmitted by the terminal 1050. Also, itbecomes unnecessary to provide a mode for a special setting forperforming a procedure for connection through wireless communicationbetween the terminal 1050 and the base station 470 on a modulated signaltransmitted by the base station 470. Accordingly, in the presentembodiment, the data transmission efficiency of wireless communicationcan be increased.

As described above, the encryption key may be an encryption key for anSSID of a wireless LAN, or may be an encryption key for limiting aconnection style, a service style, a connection range of a network, orthe like. That is, it is sufficient that an encryption key be introducedto limit something.

Embodiment 6

FIG. 25 is a diagram illustrating an example of the configuration of acommunication system in the present embodiment.

The communication system in FIG. 25 includes, for example, a basestation 2000 and the terminal 1050. The base station 2000 includes atransmission device 2001 and a radio device 2002. In FIG. 25, thecomponents that operate similarly to those in FIG. 6 or 15 are denotedby the same numerals. The communication between the radio device 2002and the radio device 453 in FIG. 25 is performed by using a radio wave,for example.

The transmission device 2001 of the base station (or AP) 2000 in FIG. 25includes, for example, a visible light source, a lighting device, alight source, or a light (hereinafter referred to as the light source104), such as an LED. First, a description will be given of an operationof the transmission device 2001 (i.e., “the portion related to a visiblelight source, a lighting device, a light source, or a light, such as anLED”).

In the transmission device 2001, the transmitter 102 receives theSSID-related information 1001-1, the encryption-key-related information1001-2, and the data 1002 as input. Based on these input signals, thetransmitter 102 generates the (light) modulated signal 103 and outputsthe modulated signal 103. The modulated signal 103 is transmitted, forexample, from the light source 104.

Next, a description will be given of the SSID-related information 1001-1and the encryption-key-related information 1001-2.

First, a description will be given of the SSID-related information1001-1.

The SSID-related information 1001-1 is information indicating the SSIDof the radio device 2002 using a radio wave of the base station 2000 inFIG. 25. That is, the transmission device 2001 is able to provide theterminal 1050 with access to the radio device 2002, which is a safewireless access destination. Accordingly, the terminal 1050 in FIG. 25is able to safely obtain information from the radio device 2002.

On the other hand, the transmission device 2001 is able to limit theterminal that accesses the radio device 2002 to a terminal positioned ina space where a light signal transmitted (emitted) by the transmissiondevice 2001 can be received.

When the terminal 1050 receives a light signal transmitted in apredetermined scheme, the terminal 1050 may determine that the notifiedSSID is the SSID of a safe base station. The terminal 1050 mayseparately perform a process of determining whether or not the notifiedSSID is safe. For example, the transmission device 2001 may transmit alight signal including a predetermined identifier, and the terminal 1050may determine, based on the received identifier, whether or not thenotified SSID is the SSID of a safe base station.

FIG. 25 illustrates a single base station 2000. For example, also when abase station (or AP) other than the base station 2000 exists, theterminal 1050 accesses the radio device 2002 of the base station 2000 byusing the SSID and the encryption key obtained from the transmissiondevice 2001 and obtains information.

Next, a description will be given of the encryption-key-relatedinformation 1001-2.

The encryption-key-related information 1001-2 is information about anencryption key that is necessary for the terminal 1050 to communicatewith the radio device 2002. The terminal 1050 obtains theencryption-key-related information 1001-2 from the transmission device2001, thereby becoming able to perform encrypted communication with theradio device 2002.

The SSID-related information 1001-1 and the encryption-key-relatedinformation 1001-2 have been described above.

The terminal 1050 in FIG. 25 receives a modulated signal transmitted bythe transmission device 2001. In the terminal 1050 in FIG. 25, thecomponents that operate similarly to those of the terminal 150 in FIG. 6or those of the terminal 1050 in FIG. 15 are denoted by the samenumerals.

The light receiver 151 included in the terminal 1050 is, for example, animage sensor, such as a CMOS sensor or an organic CMOS sensor. The lightreceiver 151 receives light including the modulated signal transmittedby the transmission device 2001 and outputs the reception signal 152.

The receiver 153 receives the reception signal 152 received by the lightreceiver 151 as input, performs processing, such as demodulation anderror-correction decoding, on the modulated signal included in thereception signal 152, and outputs the reception data 154.

The data analyzer 155 receives the reception data 154 as input andoutputs, for example, the SSID information 1051 on the radio device 2002of the base station 2000 as a connection destination and the encryptionkey information 1052 for communicating with the radio device 2002 of thebase station 2000 as the connection destination, which are included inthe reception data. For example, in a wireless local area network (LAN),Wired Equivalent Privacy (WEP), Wi-Fi Protected Access (WPA), and Wi-FiProtected Access 2 (WPA2) (Pre-Shared Key (PSK) mode, ExtendedAuthentication Protocol (EAP) mode) are available as an encryptionscheme. Note that the encryption scheme is not limited thereto.

The display 157 receives the SSID information 1051 and the encryptionkey information 1052 as input, and displays, for example, the SSID andthe encryption key of a communication partner that the radio device 453included in the terminal 1050 is to access (this display operation isreferred to as a “first display operation” in the present embodiment).

For example, after the first display operation, the radio device 453receives the SSID information 1051 and the encryption key information1052 as input, and establishes a connection with the radio device 2002of base station 2000 (for example, a radio wave is used for theconnection). At this time, when the radio device 2002 of the basestation 2000 communicates with the radio device 453 included in theterminal 1050, the radio device 2002 transmits a modulated signal byusing a radio wave, for example.

After that, the radio device 453 receives the data 1053 and the controlsignal 1054 as input, modulates the data 1053 in accordance with controlindicated by the control signal 1054, and transmits a modulated signalby using a radio wave.

Subsequently, for example, the radio device 2002 of the base station2000 performs data transmission (471) by using a network and datareception (472) by using the network. After that, for example, the radiodevice 2002 of the base station 2000 transmits a modulated signal to theterminal 1050 by using a radio wave.

The radio device 453 included in the terminal 1050 performs processing,such as demodulation and error-correction decoding, on the modulatedsignal received by using a radio wave, and obtains the reception data1056. The display 157 performs display based on the reception data 1056.

The frame configuration of the modulated signal transmitted by the radiodevice 2002 of the base station 2000 in the present embodiment issimilar to the frame configuration in FIG. 16 described in Embodiment 4.That is, in FIG. 16, the SSID-related symbol 600-1 is a symbol fortransmitting the SSID-related information 1001-1 in FIG. 25, and theencryption-key-related symbol 1101 is a symbol for transmitting theencryption-key-related information 1001-2 in FIG. 25. The data symbol1102 is a symbol for transmitting the data 1002 in FIG. 25.

As illustrated in FIG. 16, the radio device 2002 of the base station2000 transmits the preamble 201, the control information symbol 202, theSSID-related symbol 600-1, the encryption-key-related symbol 1101, andthe data symbol 1102. The radio device 2002 of the base station 2000 maytransmit a frame including a symbol other than the symbols illustratedin FIG. 16. The frame configuration, including the order in which thesymbols are transmitted, is not limited to the configuration in FIG. 16.

The frame configuration of the modulated signal transmitted by the radiodevice 453 of the base station 1050 in the present embodiment is similarto the frame configuration in FIG. 17 described in Embodiment 4. Thatis, as illustrated in FIG. 17, the radio device 453 included in theterminal 1050 in FIG. 25 transmits, for example, the preamble 1201, andthen transmits the control information symbol 1202 and the informationsymbol 1203.

At this time, the preamble 1201 is a symbol by which the radio device2002 of the base station 2000 that receives the modulated signaltransmitted by radio device 453 performs, for example, signal detection,time synchronization, frame synchronization, frequency synchronization,frequency offset estimation, and the like.

The control information symbol 1202 is a symbol including, for example,data of information about an error-correction coding scheme and amodulation scheme that are used by the terminal 1050 to generate themodulated signal, information about the frame configuration, andinformation about a transmission method. The radio device 2002 of thebase station 2000 performs demodulation or the like on the modulatedsignal based on the information included in the control informationsymbol 1202.

The information symbol 1203 is a symbol by which the radio device 453 ofthe terminal 1050 transmits data.

The radio device 453 of the terminal 1050 may transmit a frame includinga symbol other than the symbols illustrated in FIG. 17. For example, theradio device 453 may transmit a frame in which a pilot symbol (referencesymbol) is included in a middle of the information symbol 1203. Theframe configuration, including the order in which the symbols aretransmitted, is not limited to the configuration in FIG. 17. In FIG. 17,a plurality of symbols may exist in the frequency axis direction. Thatis, symbols may exist at a plurality of frequencies (a plurality ofcarriers) in FIG. 17.

The frame configuration of the modulated signal transmitted by the radiodevice 2002 in the present embodiment is similar to the frameconfiguration in FIG. 12 described in Embodiment 3. That is, asillustrated in FIG. 12, the radio device 2002 transmits, for example,the preamble 701, and then transmits the control information symbol 702and the information symbol 703.

The preamble 701 is a symbol by which the radio device 453 of theterminal 1050 that receives the modulated signal transmitted by theradio device 2002 performs, for example, signal detection, timesynchronization, frame synchronization, frequency synchronization,frequency offset estimation, and the like.

The control information symbol 702 is a symbol including, for example,data of information about an error-correction coding scheme and amodulation scheme that are used to generate the modulated signal,information about the frame configuration, and information about atransmission method. The radio device 453 of the terminal 1050 performsdemodulation or the like on the modulated signal based on theinformation of the control information symbol 702.

The information symbol 703 is a symbol by which the radio device 2002transmits data.

The radio device 2002 of the base station 2000 illustrated in FIG. 25may transmit a frame including a symbol other than the symbolsillustrated in FIG. 12. For example, the radio device 2002 may transmita frame in which a pilot symbol (reference symbol) is included in amiddle of the information symbol 703. The frame configuration, includingthe order in which the symbols are transmitted, is not limited to theconfiguration in FIG. 12. In FIG. 12, a plurality of symbols may existin the frequency axis direction. That is, symbols may exist at aplurality of frequencies (a plurality of carriers) in FIG. 12.

In addition, for example, the modulated signal that is transmitted bythe transmission device 2001 and that has the frame configuration inFIG. 16 may be repeatedly transmitted at a regular interval, forexample. Accordingly, a plurality of terminals 1050 are able to performthe above-described operation.

FIG. 26 is a flowchart illustrating an example of a process performed bythe “transmission device 2001 of the base station 2000”, the “terminal1050”, and the “radio device 2002 of the base station 2000” illustratedin FIG. 25.

First, the transmission device 2001 transmits a modulated signal havingthe frame configuration in FIG. 16 (ST1301).

Subsequently, the terminal 1050 receives the modulated signaltransmitted by the transmission device 2001 and obtains the SSID of thebase station 2000 (radio device 2002) that the terminal 1050 is toaccess (ST1302).

Also, the terminal 1050 obtains an encryption key to be used forcommunication with the base station 2000 (radio device 2002) that theterminal 1050 is to access (ST1303).

Subsequently, the terminal 1050 establishes a connection through a radiowave with the radio device 2002 of the base station 2000 (ST1304). Theestablishment of the connection between the terminal 1050 and the radiodevice 2002 of the base station 2000 is completed upon receipt of aresponse from the radio device 2002 of the base station 2000 by theterminal 1050 (ST1305).

Subsequently, the terminal 1050 transmits information on the connectiondestination to the radio device 2002 of the base station 2000 by using aradio wave (ST1306).

The radio device 2002 of the base station 2000 obtains information to betransmitted to the terminal 1050 from the network (ST1307).

Subsequently, the radio device 2002 of the base station 2000 transmitsthe obtained information to the terminal 1050 by using a radio wave, andthe terminal 1050 obtains the information (ST1308). The terminal 1050obtains necessary information from the network via the radio device 2002of the base station 2000 when necessary, for example.

As described above, based on the SSID information and the encryption keyinformation transmitted by the transmission device 2001 of the basestation 2000, the terminal 1050 establishes a connection with the radiodevice 2002 of the base station 2000 and obtains information, therebybeing able to safely obtain the information via the base station 2000that is safety-guaranteed. This is because, when the terminal 1050obtains information from a modulated signal of visible light, the useris able to easily determine whether or not the source of the informationis safe because the modulated signal is visible light. In contrast, forexample, when the SSID is obtained from a modulated signal of a radiowave transmitted through a wireless LAN, it is difficult for the user todetermine the apparatus that has transmitted the radio wave. Therefore,visible light communication is more suitable for obtaining the SSID thanwireless LAN communication in terms of ensuring the safety ofinformation.

In the present embodiment, a description has been given of a case wherethe transmission device 2001 transmits encryption key information.However, for example, when the radio device 2002 of the base station2000 does not perform encrypted communication using an encryption key,it is sufficient that the transmission device 2001 transmit onlySSID-related information, not encryption key information. In this case,a similar operation can be performed only by removing the componentrelated to the encryption key among the components of the transmissiondevice 2001.

As illustrated in FIG. 25, the SSID and the encryption key of the radiodevice 2002 of the base station 2000 may be configured to be rewritable.For example, in FIG. 25, the SSID-related information 1001-1 and theencryption-key-related information 1001-2 are input to the radio device2002. The radio device 2002 of the base station 2000 rewrites the SSIDand the encryption key by using the SSID-related information 1001-1 andthe encryption-key-related information 1001-2 that have been input.Accordingly, the safety of the communication between the terminal 1050and the radio device 2002 of the base station 2000 is further ensured.In FIG. 25, the radio device 2002 of the base station 2000 has afunction of rewriting the SSID and the encryption key, but the radiodevice 2002 may be unable to rewrite both or either of the SSID and theencryption key.

The configuration of the transmission device is not limited to theconfiguration of the transmission device 2001 illustrated in FIG. 25,the configuration of the terminal is not limited to the configuration ofthe terminal 1050 illustrated in FIG. 25, and the connection destinationand the configuration of the radio device are not limited to theconnection destination and the configuration of the radio device 2002illustrated in FIG. 25.

FIG. 25 illustrates a case where there is a single base station 2000,but there may be radio devices 2002 of a plurality of base stations (orAPs) 2000 accessible to the terminal 1050 (safe base stations). Theradio devices 2002 of the plurality of base stations 2000 and theterminal 1050 each transmit/receive a modulated signal by using a radiowave. At this time, the SSID-related symbol transmitted by thetransmission device 2001 in FIG. 25 may include information indicatingthe SSIDs of the radio devices 2002 of the plurality of base stations2000. The encryption-key-related symbol transmitted by the transmissiondevice 2001 in FIG. 25 may include information indicating the encryptionkeys that are used to connect to the radio devices 2002 of the pluralityof base stations 2000. Based on the information indicating the SSIDs andencryption keys of the radio devices 2002 of the plurality of basestations 2000, the terminal 1050 in FIG. 25 may select the radio device2002 of the base station 2000 to be connected in a wireless manner (forexample, by using a radio wave) (or may establish connections with theradio devices of the plurality of base stations).

For example, it is assumed that there are three base stations 2000 eachincluding the radio device 2002. Here, the radio devices 2002 of thethree base stations 2000 are referred to as a radio device #A, a radiodevice #B, and a radio device #C. Also, it is assumed that the SSID ofthe radio device #A is “abcdef”, the SSID of the radio device #B is“ghijk”, and the SSID of the radio device #C is “pqrstu”. Also, it isassumed that the encryption key for connecting to the radio device #A is“123”, the radio device for connecting to the radio device #B is “456”,and the encryption key for connecting to the radio device #C is “789”.

In this case, the SSID-related symbol 600-1 in the frame configurationin FIG. 16 of the modulated signal transmitted by the transmissiondevice 2001 includes information indicating that “the SSID of the radiodevice #A is ‘abcdef’”, “the SSID of the radio device #B is ‘ghijk’”,and “the SSID of the radio device #C is ‘pqrstu’”. Theencryption-key-related symbol 1101 in the frame configuration in FIG. 16includes information indicating that “the encryption key for connectingto the radio device #A is ‘123’”, “the encryption key for connecting tothe radio device #B is ‘456’”, and “the encryption key for connecting tothe radio device #C is ‘789’”.

The terminal 1050 in FIG. 25 receives the SSID-related symbol 600-1 andobtains the information indicating that “the SSID of the radio device #Ais ‘abcdef’”, “the SSID of the radio device #B is ‘ghijk’”, and “theSSID of the radio device #C is ‘pqrstu’”. Also, the terminal 1050receives the encryption-key-related symbol 1101 and obtains theinformation indicating that “the encryption key for connecting to theradio device #A is ‘123’”, “the encryption key for connecting to theradio device #B is ‘456’”, and “the encryption key for connecting to theradio device #C is ‘789’”. Based on these pieces of information, theterminal 1050 selects a base station to be connected in a wirelessmanner (for example, by using a radio wave), and establishes theconnection.

As in the present embodiment, with the radio device 2002 of the basestation 2000 to be accessed by the terminal 1050 being set by using alight source, such as an LED, it becomes unnecessary to provide a modefor a special setting for performing a procedure for connection throughwireless communication between the terminal 1050 and the base station2000 on a modulated signal for wireless communication transmitted by theterminal 1050. Also, it becomes unnecessary to provide a mode for aspecial setting for performing a procedure for connection throughwireless communication between the terminal 1050 and the base station2000 on a modulated signal transmitted by the base station 2000.Accordingly, in the present embodiment, the data transmission efficiencyof wireless communication can be increased.

As described above, the encryption key may be an encryption key for anSSID of a wireless LAN, or may be an encryption key for limiting aconnection style, a service style, a connection range of a network, orthe like. That is, it is sufficient that an encryption key be introducedto limit something.

Embodiment 7

FIG. 27 is a diagram illustrating an example of the configuration of acommunication system in the present embodiment.

The communication system in FIG. 27 includes the apparatus 1000, theterminal 1050, and a base station (or AP) 470-1 (base station #1), abase station (or AP) 470-2 (base station #2), and a base station (or AP)470-3 (base station #3) that communicates with the terminal 1050. InFIG. 27, the components that operate similarly to those in FIG. 6, 9, or15 are denoted by the same numerals.

The apparatus 1000 includes, for example, a visible light, a lightingdevice, a light source, or a light (light source 104), such as an LED.Hereinafter, the apparatus 1000 will be referred to as a “fifthapparatus” in the present embodiment. It is assumed that thecommunication between the radio device 453 and the base station 470-1(base station #1), the communication between the radio device 453 andthe base station 470-2 (base station #2), and the communication betweenthe radio device 453 and the base station 470-3 (base station #3) inFIG. 27 are performed by using a radio wave, for example.

In the fifth apparatus 1000 in FIG. 27, the transmitter 102 receives theSSID-related information 1001-1, the encryption-key-related information1001-2, and the data 1002 as input, generates the (light) modulatedsignal 103 based on these input signals, and outputs the modulatedsignal 103. The modulated signal 103 is transmitted, for example, fromthe light source 104.

Next, a description will be given of the SSID-related information 1001-1and the encryption-key-related information 1001-2.

First, a description will be given of the SSID-related information1001-1.

The SSID-related information 1001-1 includes, for example, informationindicating the SSID of the base station 470-1 (base station #1),information indicating the SSID of the base station 470-2 (base station#2), and information indicating the SSID of the base station 470-3 (basestation #3) in FIG. 27. For example, each of the base stations 470-1,470-2, and 470-3 transmits a modulated signal by using a radio wave andreceives a modulated signal, which is a radio wave. That is, the fifthapparatus 1000 is able to provide the terminal 1050 with access to thebase stations 470-1, 470-2, and 470-3, which are safe accessdestinations. Accordingly, the terminal 1050 in FIG. 27 is able tosafely obtain information from the base stations 470-1, 470-2, and470-3.

On the other hand, the fifth apparatus 1000 is able to limit theterminal that accesses the base stations 470-1, 470-2, and 470-3 to aterminal positioned in a space where a light signal transmitted(emitted) by the fifth apparatus 1000 can be received.

When the terminal 1050 receives a light signal transmitted in apredetermined scheme, the terminal 1050 may determine that the notifiedSSID is the SSID of a safe base station. The terminal 1050 mayseparately perform a process of determining whether or not the notifiedSSID is safe. For example, the fifth apparatus 1000 may transmit a lightsignal including a predetermined identifier, and the terminal 1050 maydetermine, based on the received identifier, whether or not the notifiedSSID is the SSID of a safe base station.

In FIG. 27, there are the base stations 470-1, 470-2, and 470-3. Forexample, there may be a base station (or AP) other than the basestations 470-1, 470-2, and 470-3.

Next, a description will be given of the encryption-key-relatedinformation 1001-2.

The encryption-key-related information 1001-2 is information about anencryption key that is necessary for the terminal 1050 to communicatewith the base stations 470-1, 470-2, and 470-3. The terminal 1050obtains the encryption-key-related information 1001-2 from the fifthapparatus 1000, thereby becoming able to perform encrypted communication“between the terminal 1050 and the base station 470-1”, “between theterminal 1050 and the base station 470-2”, and “between the terminal1050 and the base station 470-3”.

The SSID-related information 1001-1 and the encryption-key-relatedinformation 1001-2 have been described above.

The terminal 1050 in FIG. 27 receives a modulated signal transmitted bythe fifth apparatus 1000. In the terminal 1050 in FIG. 27, thecomponents that operate similarly to those of the terminal 150 in FIG. 6or those of the terminal 450 in FIG. 9 are denoted by the same numerals.

The light receiver 151 included in the terminal 1050 is, for example, animage sensor, such as a CMOS sensor or an organic CMOS sensor. The lightreceiver 151 receives light including the modulated signal transmittedby the fifth apparatus 1000 and outputs the reception signal 152.

The receiver 153 receives the reception signal 152 received by the lightreceiver 151 as input, performs processing, such as demodulation anderror-correction decoding, on the modulated signal included in thereception signal 152, and outputs the reception data 154.

The data analyzer 155 receives the reception data 154 as input andoutputs, for example, the SSID information 1051 on the base stations470-1, 470-2, and 470-3 as connection destinations and the encryptionkey information 1052 for communicating with the base stations 470-1,470-2, and 470-3 as the connection destinations, which are included inthe reception data 154. For example, in a wireless local area network(LAN), Wired Equivalent Privacy (WEP), Wi-Fi Protected Access (WPA), andWi-Fi Protected Access 2 (WPA2) (Pre-Shared Key (PSK) mode, ExtendedAuthentication Protocol (EAP) mode) are available as an encryptionscheme. Note that the encryption scheme is not limited thereto.

The display 157 receives the SSID information 1051 and the encryptionkey information 1052 as input, and displays, for example, the SSID andthe encryption key of a communication partner that the radio device 453included in the terminal 1050 is to access (this display operation isreferred to as a “first display operation” in the present embodiment).

For example, after the first display operation, the radio device 453receives the SSID information 1051 and the encryption key information1052 as input, and establishes a connection with any of the basestations 470-1, 470-2, and 470-3 (for example, a radio wave is used forthe connection). At this time, when the connected base station 470communicates with the radio device 453 included in the terminal 1050,the base station 470 transmits a modulated signal by using a radio wave,for example.

After that, the radio device 453 receives the data 1053 and the controlsignal 1054 as input, modulates the data 1053 in accordance with controlindicated by the control signal 1054, and transmits a modulated signalas a radio wave.

Subsequently, for example, the connected base station 470 performs datatransmission (any of 471-1, 471-2, and 471-3) by using a network anddata reception (472-1, 472-2, and 472-3) by using the network. Afterthat, for example, the connected base station 470 transmits a modulatedsignal to the terminal 1050 by using a radio wave.

The radio device 453 included in the terminal 1050 performs processing,such as demodulation and error-correction decoding, on the modulatedsignal received by using a radio wave, and obtains the reception data1056. The display 157 performs display based on the reception data 1056.

In the case of FIG. 27, there are three types of frame configurations ofthe modulated signal transmitted by the fifth apparatus 1000. FIG. 28illustrates a frame 2300-1 (frame #1), which is one of the three typesof frame configurations, FIG. 29 illustrates a frame 2300-2 (frameconfiguration #2), which is one of the three types of frameconfigurations, and FIG. 30 illustrates a frame 2300-3 (frameconfiguration #3), which is one of the three types of frameconfigurations.

FIG. 28 illustrates an example of the configuration of the frame 2300-1(frame #1) of the modulated signal transmitted by the fifth apparatus1000. In FIG. 28, the horizontal axis indicates time. In FIG. 28, thesymbols similar to those in FIG. 2 or 16 are denoted by the samenumerals, and the description thereof is omitted. The frame 2300-1(frame #1) in FIG. 28 is a frame for transmitting information on theSSID of the base station 470-1 (base station #1) in FIG. 27 andinformation on the encryption key of the base station 470-1 (basestation #1) (the encryption key for accessing the base station 470-1).

An SSID-related symbol 2301-1 is a symbol for transmitting theSSID-related information 1001-1 in FIG. 27. The SSID-related symbol2301-1 is a symbol by which the fifth apparatus 1000 in FIG. 27transmits the SSID of the base station 470-1 (base station #1).

A encryption-key-related symbol 2302-1 is a symbol for transmitting theencryption-key-related information 1001-2 in FIG. 27. Theencryption-key-related symbol 2302-1 is a symbol by which the fifthapparatus 1000 in FIG. 27 transmits the encryption key of the basestation 470-1 (base station #1) (the encryption key for accessing thebase station 470-1).

The fifth apparatus 1000 transmits the preamble 201, the controlinformation symbol 202, the SSID-related symbol 2301-1, theencryption-key-related symbol 2302-1, and the data symbol 1102. Thefifth apparatus 1000 may transmit the frame 2300-1 (frame #1) includinga symbol other than the symbols illustrated in FIG. 28. Theconfiguration of the frame 2300-1 (frame #1), including the order inwhich the symbols are transmitted, is not limited to the configurationin FIG. 28.

FIG. 29 illustrates an example of the configuration of the frame 2300-2(frame #2) of the modulated signal transmitted by the fifth apparatus1000. In FIG. 29, the horizontal axis indicates time. In FIG. 29, thesymbols similar to those in FIG. 2 or 16 are denoted by the samenumerals, and the description thereof is omitted. The frame 2300-2(frame #2) in FIG. 29 is a frame for transmitting information on theSSID of the base station 470-2 (base station #2) in FIG. 27 andinformation on the encryption key of the base station 470-2 (basestation #2) (the encryption key for accessing the base station 470-2).

An SSID-related symbol 2301-2 is a symbol for transmitting theSSID-related information 1001-1 in FIG. 27. The SSID-related symbol2301-2 is a symbol by which the fifth apparatus 1000 in FIG. 27transmits the SSID of the base station 470-2 (base station #2).

A encryption-key-related symbol 2302-2 is a symbol for transmitting theencryption-key-related information 1001-2 in FIG. 27. Theencryption-key-related symbol 2302-2 is a symbol by which the fifthapparatus 1000 in FIG. 27 transmits the encryption key of the basestation 470-2 (base station #2) (the encryption key for accessing thebase station 470-2).

The fifth apparatus 1000 transmits the preamble 201, the controlinformation symbol 202, the SSID-related symbol 2301-2, theencryption-key-related symbol 2302-2, and the data symbol 1102. Thefifth apparatus 1000 may transmit the frame 2300-2 (frame #2) includinga symbol other than the symbols illustrated in FIG. 29. Theconfiguration of the frame 2300-2 (frame #2), including the order inwhich the symbols are transmitted, is not limited to the configurationin FIG. 29.

FIG. 30 illustrates an example of the configuration of the frame 2300-3(frame #3) of the modulated signal transmitted by the fifth apparatus1000. In FIG. 30, the horizontal axis indicates time. In FIG. 30, thesymbols similar to those in FIG. 2 or 16 are denoted by the samenumerals, and the description thereof is omitted. The frame 2300-3(frame #3) in FIG. 30 is a frame for transmitting information on theSSID of the base station 470-3 (base station #3) in FIG. 27 andinformation on the encryption key of the base station 470-3 (basestation #3) (the encryption key for accessing the base station 470-3).

An SSID-related symbol 2301-3 is a symbol for transmitting theSSID-related information 1001-1 in FIG. 27. The SSID-related symbol2301-3 is a symbol by which the fifth apparatus 1000 in FIG. 27transmits the SSID of the base station 470-3 (base station #3).

A encryption-key-related symbol 2302-3 is a symbol for transmitting theencryption-key-related information 1001-2 in FIG. 27. Theencryption-key-related symbol 2302-3 is a symbol by which the fifthapparatus 1000 transmits the encryption key of the base station 470-3(base station #3) (the encryption key for accessing the base station470-3).

The fifth apparatus 1000 transmits the preamble 201, the controlinformation symbol 202, the SSID-related symbol 2301-3, theencryption-key-related symbol 2302-3, and the data symbol 1102. Thefifth apparatus 1000 may transmit the frame 2300-3 (frame #3) includinga symbol other than the symbols illustrated in FIG. 30. Theconfiguration of the frame 2300-3 (frame #3), including the order inwhich the symbols are transmitted, is not limited to the configurationin FIG. 30.

FIG. 31 illustrates an example of a transmission method in which thefifth apparatus 1000 transmits “frame 2300-1 (frame #1) in FIG. 28”,“frame 2300-2 (frame #2) in FIG. 29”, and “frame 2300-3 (frame #3) inFIG. 30”. In FIG. 31, the horizontal axis indicates time.

Referring to FIG. 31, in “frame #1 group transmission” 2601-1 and2601-2, one or more frames 2300-1 (frames #1), each being the one inFIG. 28, are transmitted. In “frame #2 group transmission” 2602-1 and2602-2, one or more frames 2300-2 (frames #2), each being the one inFIG. 29, are transmitted. In “frame #3 group transmission” 2603-1 and2603-2, one or more frames 2300-3 (frames #3), each being the one inFIG. 30, are transmitted.

A detailed description of this case will be described below.

First, a description will be given of “frame #1 group transmission”2601-1 and 2601-2 in which one or more frames 2300-1 (frames #1), eachbeing the one in FIG. 28, are transmitted.

For example, when an image sensor, such as a CMOS sensor or an organicCMOS sensor, is used in the light receiver 151, there is a possibilitythat a reception signal is processed in units of frames in a video orstill image. For example, “4K30p” in a video means that the number ofpixels per frame is 3840×2160 and that the number of frames per secondis 30.

Thus, when the fifth apparatus 1000 transmits a modulated signal havinga configuration in which one frame includes “frame 2300-1 (frame #1) inFIG. 28”, “frame 2300-2 (frame #2) in FIG. 29”, and “frame 2300-3 (frame#3) in FIG. 30”, it is difficult for the terminal 1050 in FIG. 27 toselect the base station 470 to be accessed from among the plurality ofbase stations 470-1, 470-2, and 470-3.

Accordingly, in the present embodiment, the frame configurationillustrated in FIG. 31 is proposed.

<Method 1-1>

In method 1-1, a plurality of frames 2300-1 (frames #1), each being theone in FIG. 28, are included in each of “frame #1 group transmission”2601-1 and 2601-2, so that the time section occupied by each of “frame#1 group transmission” 2601-1 and 2601-2 is longer than that of a framein a video or still image.

Accordingly, the terminal 1050 is able to prevent receiving, from thefifth apparatus 1000, a modulated signal in which one frame in a videoor still image includes “frame 2300-1 (frame #1) in FIG. 28”, “frame2300-2 (frame #2) in FIG. 29”, and “frame 2300-3 (frame #3) in FIG. 30”,that is, different SSIDs and encryption keys. Thus, the terminal 1050 inFIG. 27 is able to easily select the base station 470 to be accessedfrom among the plurality of base stations 470-1, 470-2, and 470-3.

<Method 2-1>

In method 2-1, the time section occupied by the frame 2300-1 (frame #1)in FIG. 28 is made longer than that of a frame in a video or stillimage.

For example, the SSID-related symbol 2301-1 in FIG. 28 may include aplurality of pieces of “base station #1 SSID information” (i.e., “basestation #1 SSID information” is repeatedly included), and theencryption-key-related symbol 2302-1 may include a plurality of piecesof “base station #1 encryption key information (information on theencryption key for connecting to the base station #1)” (i.e. “basestation #1 encryption key information (information on the encryption keyfor connecting to the base station #1)” is repeatedly included).

Accordingly, the terminal 1050 is able to prevent receiving, from thefifth apparatus 1000, a modulated signal in which one frame in a videoor still image includes “frame 2300-1 (frame #1) in FIG. 28”, “frame2300-2 (frame #2) in FIG. 29”, and “frame 2300-3 (frame #3) in FIG. 30”,that is, different SSIDs and encryption keys. Thus, the terminal 1050 isable to easily select the base station 470 to be accessed from among theplurality of base stations 470-1, 470-2, and 470-3.

Similarly, “frame #2 group transmission” 2602-1 and 2602-2 may have thefollowing configuration.

<Method 1-2>

In method 1-2, a plurality of frames 2300-2 (frames #2), each being theone in FIG. 29, are included in each of “frame #2 group transmission”2602-1 and 2602-2, so that the time section occupied by “frame #2 grouptransmission” is longer than that of a frame in a video or still image.

<Method 2-2>

In method 2-2, the time section occupied by the frame 2300-2 (frame #2)in FIG. 29 is made longer than that of a frame in a video or stillimage.

For example, the SSID-related symbol 2301-2 in FIG. 29 may include aplurality of pieces of “base station #2 SSID information” (i.e., “basestation #2 SSID information” is repeatedly included), and theencryption-key-related symbol 2302-2 may include a plurality of piecesof “base station #2 encryption key information (information on theencryption key for connecting to the base station #2)” (i.e. “basestation #2 encryption key information (information on the encryption keyfor connecting to the base station #2)” is repeatedly included).

Similarly, “frame #3 group transmission” 2603-1 and 2603-2 may have thefollowing configuration.

<Method 1-3>

In method 1-3, a plurality of frames 2300-3 (frames #3), each being theone in FIG. 30, are included in each of “frame #3 group transmission”2603-1 and 2603-2, so that the time section occupied by “frame #3 grouptransmission” is longer than that of a frame in a video or still image.

<Method 2-3>

In method 2-3, the time section occupied by the frame 2300-3 (frame #3)in FIG. 30 is made longer than that of a frame in a video or stillimage.

For example, the SSID-related symbol 2301-3 in FIG. 30 may include aplurality of pieces of “base station #3 SSID information” (i.e., “basestation #3 SSID information” is repeatedly included), and theencryption-key-related symbol 2302-3 may include a plurality of piecesof “base station #3 encryption key information (information on theencryption key for connecting to the base station #3)” (i.e. “basestation #3 encryption key information (information on the encryption keyfor connecting to the base station #3)” is repeatedly included).

Next, a description will be given of an effect in a case where the fifthapparatus 1000 transmits frames in the manner illustrated in FIGS. 28 to31.

For example, an area 2700 in FIG. 32 is considered. In FIG. 32, thefifth apparatus 1000 is located at each of the positions of singlecircles 2701-1, 2701-2, 2701-3, 2701-4, 2701-5, 2701-6, 2701-7, 2701-8,2701-9, and 2701-10. Also, the base station 470-1 (base station #1) islocated at the position of a double circle 2702-1, the base station470-2 (base station #2) is located at the position of a double circle2702-2, and the base station 470-3 (base station #3) is located at theposition of a double circle 2702-3.

In addition, for example, it is assumed that there are 99 terminals,each having a configuration similar to the configuration of the terminal1050, (hereinafter simply referred to as terminals 1050) in an area2703.

At this time, for example, both the fifth apparatuses 1000 located atthe positions of the single circles 2701-5 and 2701-10 transmitinformation on the SSID of the base station 470-3 (base station #3) andtransmit information on the encryption key for accessing the basestation 470-3 (base station #3). This is because the base station thatis the nearest to the positions of the single circles 2701-5 and 2701-10is the base station 470-3 (base station #3).

In this case, all the 99 terminals 1050 access the base station 470-3(base station #3). Accordingly, the access concentration increases thepossibility that there is a terminal 1050 having difficulty in accessingthe base station 470-3 (base station #3).

Taking this point into consideration, the number of terminals 1050having difficulty in accessing the base station 470 as described abovecan be reduced by performing control to allow the 99 terminals 1050 toaccess the base station 470-1 (base station #1) (the position of thesingle circle 2702-1), the base station 470-2 (base station #2) (theposition of the single circle 2702-2), and the base station 470-3 (basestation #3) (the position of the single circle 2702-3) as evenly aspossible.

For example, the timings at which the 99 terminals 1050 access the fifthapparatus 1000 are typically different. Thus, as in the presentembodiment, when the fifth apparatus 1000 transmits frames in the mannerillustrated in FIGS. 28 to 31, each of the 99 terminals 1050 obtains theSSID and the encryption key of any one of the base stations 470-1,470-2, and 470-3 in accordance with the timing to access the fifthapparatus 1000. Accordingly, “control to allow the 99 terminals 1050 toaccess the base stations 470-1, 470-2, and 470-3 as evenly as possible”is performed. Accordingly, the number of terminals 1050 havingdifficulty in accessing the base station 470 described above can bereduced.

FIG. 31 illustrates an example of a transmission method in which thefifth apparatus 1000 transmits “frame 2300-1 (frame #1) in FIG. 28”,“frame 2300-2 (frame #2) in FIG. 29”, and “frame 2300-3 (frame #3) inFIG. 30”. However, the transmission method in which the fifth apparatus1000 transmits “frame 2300-1 (frame #1) in FIG. 28”, “frame 2300-2(frame #2) in FIG. 29”, and “frame 2300-3 (frame #3) in FIG. 30” is notlimited thereto.

For example, FIG. 31 illustrates a configuration in which the fifthapparatus 1000 repeatedly performs transmission in the order of “frame#1 group transmission”, “frame #2 group transmission”, and “frame #3group transmission”. However, “frame #1 group transmission”, “frame #2group transmission”, and “frame #3 group transmission” need notnecessarily be performed in the order illustrated in FIG. 31.Alternatively, for example, the fifth apparatus 1000 may perform “frame#1 group transmission”, “frame #2 group transmission”, and “frame #3group transmission” temporarily randomly, or may perform “frame #1 grouptransmission”, “frame #2 group transmission”, and “frame #3 grouptransmission” in a regular order different from the order in FIG. 31. Itis sufficient that the fifth apparatus 1000 at least perform “frame #1group transmission”, “frame #2 group transmission”, and “frame #3 grouptransmission”.

In FIG. 31, the fifth apparatus 1000 consecutively performs “frame #1group transmission”, “frame #2 group transmission”, and “frame #3 grouptransmission”, but such consecutive transmission need not necessarily beperformed. For example, in FIG. 31, there may be a time interval betweenthe frame #1 group 2601-1 and the frame #2 group transmission 2602-2.

In FIG. 31, there are only “frame #1 group transmission”, “frame #2group transmission”, and “frame #3 group transmission”, but there may beother symbols and other frames. Furthermore, in FIGS. 31 and 27, thenumber of base stations 470 is three, but the number of base stations470 is not limited thereto. Also when the number of base stations 470 istwo or more, an operation similar to that when the number of basestations 470 is three can be performed. Thus, for example, when thenumber of base stations 470 is N (N is n integer greater than or equalto 2) and the fifth apparatus 1000 performs the transmission asillustrated in FIG. 31, “frame #k group transmission” is performed. Notethat k is an integer greater than or equal to 1 and smaller than orequal to N. Also, “frame #k group transmission” includes an SSID-relatedsymbol (information on the SSID of a base station #k) and includes aencryption-key-related symbol (information on the encryption key foraccessing the base station #k).

The frame configuration of the modulated signal transmitted by the radiodevice 453 included in the terminal 1050 in FIG. 27 is similar to theframe configuration in FIG. 17 described in Embodiment 4. That is, asillustrated in FIG. 17, the radio device 453 included in the terminal1050 in FIG. 27 transmits, for example, the preamble 1201, and thentransmits the control information symbol 1202 and the information symbol1203.

The preamble 1201 is a symbol by which the base stations 470-1, 470-2,and 470-3 that receive the modulated signal transmitted by radio device453 of the terminal 1050 perform, for example, signal detection, timesynchronization, frame synchronization, frequency synchronization,frequency offset estimation, and the like.

The control information symbol 1202 is a symbol including, for example,data of information about an error-correction coding scheme and amodulation scheme that are used to generate the modulated signal,information about the frame configuration, and information about atransmission method. The base stations 470-1, 470-2, and 470-3 performdemodulation or the like on the modulated signal based on theinformation included in the control information symbol 1202.

The information symbol 1203 is a symbol by which the radio device 453 ofthe terminal 1050 transmits data.

The radio device 453 of the terminal 1050 in FIG. 27 may transmit aframe including a symbol other than the symbols illustrated in FIG. 17(for example, a frame in which a pilot symbol (reference symbol) isincluded in a middle of the information symbol 1203). The frameconfiguration, including the order in which the symbols are transmitted,is not limited to the configuration in FIG. 17. In FIG. 17, a pluralityof symbols may exist in the frequency axis direction. That is, symbolsmay exist at a plurality of frequencies (a plurality of carriers).

The frame configuration of the modulated signal transmitted by the basestations 470-1, 470-2, and 470-3 in FIG. 27 is similar to the frameconfiguration in FIG. 12 described in Embodiment 3. That is, asillustrated in FIG. 12, the base stations 470-1, 470-2, and 470-3transmit, for example, the preamble 701, and then transmit the controlinformation symbol 702 and the information symbol 703.

The preamble 701 is a symbol by which the radio device 453 of theterminal 1050 that receives the modulated signals transmitted by thebase stations 470-1, 470-2, and 470-3 performs, for example, signaldetection, time synchronization, frame synchronization, frequencysynchronization, frequency offset estimation, and the like.

The control information symbol 702 is a symbol including, for example,data of information about an error-correction coding scheme and amodulation scheme that are used to generate the modulated signal,information about the frame configuration, and information about atransmission method. The radio device 453 of the terminal 1050 performsdemodulation or the like on the modulated signal based on theinformation of the control information symbol 702.

The information symbol 703 is a symbol by which the base stations 470-1,470-2, and 470-3 transmit data.

The base stations 470-1, 470-2, and 470-3 may transmit a frame includinga symbol other than the symbols illustrated in FIG. 12. For example, thebase stations 470-1, 470-2, and 470-3 may transmit a frame in which apilot symbol (reference symbol) is included in a middle of theinformation symbol 703. The frame configuration, including the order inwhich the symbols are transmitted, is not limited to the configurationin FIG. 12. In FIG. 12, a plurality of symbols may exist in thefrequency axis direction. That is, symbols may exist at a plurality offrequencies (a plurality of carriers) in FIG. 12.

FIG. 33 is a flowchart illustrating an example of a process performed bythe “fifth apparatus 1000”, the “terminal 1050”, and the “base station#X”. X is 1, 2, or 3.

First, the fifth apparatus 1000 transmits a modulated signal having theframe configuration in FIG. 31 (ST2801).

The terminal 1050 receives the modulated signal transmitted by the fifthapparatus 1000 and selects the base station that the terminal 1050 is toaccess from among the base station 470-1 (base station #1), the basestation 470-2 (base station #2), and the base station 470-3 (basestation #3) in FIG. 27 (ST2802).

Hereinafter, this point will be described. The terminal 1050 receivesthe modulated signal transmitted by the fifth apparatus 1000 to accessany of the base stations 470. At this time, the terminal 1050 obtainsany of “frame #1 group transmission”, “frame #2 group transmission”, and“frame #3 group transmission” in FIG. 31 in a certain frame of a videoor still image, for example. Subsequently, the terminal 1050 determinesany of the base station 470-1 (base station #1), the base station 470-2(base station #2), and the base station 470-3 (base station #3) as thebase station 470 that the terminal 1050 is to access, based on theobtained information on the base station (for example, the SSID).

Subsequently, the terminal 1050 receives the modulated signaltransmitted by the fifth apparatus 1000 and obtains the SSID of the basestation #X that the terminal 1050 is to access (ST2803).

Also, the terminal 1050 obtains the encryption key that is used forcommunication with the base station #X that the terminal 1050 is toaccess (ST2804).

Subsequently, the terminal 1050 establishes a connection through a radiowave with the base station #X (ST2805). Upon receipt of a response fromthe base station #X by the terminal 1050, the establishment of theconnection between the terminal 1050 and the base station #X iscompleted (ST2806).

Subsequently, the terminal 1050 transmits information on the connectiondestination to the base station #X by using a radio wave (ST2807).

The base station #X obtains information to be transmitted to theterminal 1050 through a network (ST2808).

Subsequently, the base station #X transmits the obtained information tothe terminal 1050 by using a radio wave, and the terminal 1050 obtainsthe information (ST2809). The terminal 1050 obtains necessaryinformation through the network via the base station #X when necessary,for example.

As described above, based on the SSID information and the encryption keyinformation transmitted by the fifth apparatus 1000, the terminal 1050establishes a connection with the base station 470 and obtainsinformation, thereby being able to safely obtain the information via thebase station 470 that is safety-guaranteed. This is because, when theterminal 1050 obtains information from a modulated signal of visiblelight, the user is able to easily determine whether or not the source ofthe information is safe because the modulated signal is visible light.In contrast, for example, when the SSID is obtained from a modulatedsignal of a radio wave transmitted through a wireless LAN, it isdifficult for the user to determine the apparatus that has transmittedthe radio wave. Therefore, visible light communication is more suitablefor obtaining the SSID than wireless LAN communication in terms ofensuring the safety of information.

In the present embodiment, a description has been given of a case wherethe fifth apparatus 1000 transmits encryption key information. However,for example, when the base station 470 does not perform encryptedcommunication using an encryption key, it is sufficient that the fifthapparatus 1000 transmit only SSID-related information, not encryptionkey information. In this case, a similar operation can be performed onlyby removing the component related to the encryption key among theabove-described components.

The configuration of the fifth apparatus is not limited to theconfiguration of the fifth apparatus 1000 illustrated in FIG. 27, theconfiguration of the terminal is not limited to the configuration of theterminal 1050 illustrated in FIG. 27, and the connection destinationsand the configurations of the base stations #1, #2, and #3 are notlimited to the connection destinations and the configurations of thebase stations 470-1, 470-2, and 470-3 illustrated in FIG. 27.

According to the present embodiment, even when there are a plurality ofterminals 1050 in a certain area, the number of terminals 1050 havingdifficulty in accessing the base station 470 can be reduced.

In FIG. 32, all the frame configurations of the modulated signalstransmitted by the fifth apparatuses 1000 located at the positions ofthe single circles 2701-1, 2701-2, 2701-3, 2701-4, 2701-5, 2701-6,2701-7, 2701-8, 2701-9, and 2701-10 may be similar to the configurationin FIG. 31, or the frame configurations of the modulated signalstransmitted by the fifth apparatuses 1000 may be different from eachother, or there may be a plurality of fifth apparatuses 1000 thattransmit modulated signals of the same frame configuration.

Embodiment 8

In the present embodiment, a description will be given of a case wherethe above-described communication system is applied to the inside of anaircraft.

Hereinafter, it is assumed that a seat area in an aircraft is divided inaccordance with classes of services provided to passengers. For example,hereinafter, it is assumed that the seat area is divided into areasassociated with three classes: a class of higher-level services (forexample, first class), a class of middle-level services (for example,business class), and a class of lower-level services (for example,economy class). The categorization of service classes is not limitedthereto. For example, the service classes may be categorized morefinely.

As illustrated in FIG. 34, the seat area in the aircraft is divided intoan area #1 including seats for passengers provided with higher-levelservices, an area #2 including seats for passengers provided withmiddle-level services, and an area #3 including seats for passengersprovided with lower-level services.

In the following application examples, an apparatus, a terminal, and anAP (base station) constituting a communication system may have aconfiguration similar to that of, for example, the apparatus 400, 1000,1400, or 2001, the terminal 450 or 1050, and the AP (base station, radiodevice) 470 or 2002 illustrated in FIGS. 9, 15, 19, 25, and 27,respectively.

That is, the apparatuses in the present embodiment (for example,apparatuses #1, #2, and #3) each transmit (emit) a light signalincluding the SSID (identifier) of at least one AP (base station). Theterminals in the present embodiment (for example, terminals #1, #2, and#3) each receive the light signal emitted by the apparatus, selects oneAP based on the SSID included in the light signal, establishes awireless connection with the AP by using the SSID of the selected AP,and performs wireless communication. The AP (base station) in thepresent embodiment wirelessly communicates with a terminal, and alsocommunicates with various servers via a network within the aircraft(local network) or a network outside the aircraft (for example, theInternet).

Application Example 1

In Application Example 1, as illustrated in FIG. 34, one or more APs #1supporting a first wireless LAN scheme are installed in the area #1, oneor more APs #2 supporting a second wireless LAN scheme are installed inthe area #2, and one or more APs #3 supporting a third wireless LANscheme are installed in the area #3. Each AP is associated with theclass of services provided in the area in which the AP is installed.

It is assumed that the maximum transmission speed of the first wirelessLAN scheme is higher than the maximum transmission speed of the secondwireless LAN scheme, and that the maximum transmission speed of thesecond wireless LAN scheme is higher than the maximum transmission speedof the third wireless LAN scheme. That is, as the rank of a classproviding services increases, the maximum transmission speed of thewireless LAN scheme (wireless communication scheme) supported by the APassociated with the class increases.

For example, in Application Example 1, the first wireless LAN scheme maysupport IEEE 802.11ac, IEEE 802.11n, IEEE 802.11a, IEEE 802.11g, andIEEE 802.11b, the second wireless LAN scheme may support IEEE 802.11n,IEEE 802.11a, IEEE 802.11g, and IEEE 802.11b, and the third wireless LANscheme may support IEEE 802.11a, IEEE 802.11g, and IEEE 802.11b.

That is, in Application Example 1, a wireless LAN scheme supported by acertain AP includes a wireless LAN scheme supported by an AP associatedwith a lower class than a service class associated with the certain AP.Specifically, the first wireless LAN scheme includes the standardssupported by the second wireless LAN scheme and the third wireless LANscheme, and the second wireless LAN scheme includes the standardssupported by the third wireless LAN scheme. Note that examples of thestandards supported by the first wireless LAN scheme, the standardssupported by the second wireless LAN scheme, and the standards supportedby the third wireless LAN scheme are not limited to the above-describedstandards.

As illustrated in FIG. 34, one or more apparatuses #1, each including avisible light, a lighting device, a light source, or a light, such as anLED, are installed in the area #1. One or more apparatuses #2, eachincluding a visible light, a lighting device, a light source, or alight, such as an LED, are installed in the area #2. One or moreapparatuses #3, each including a visible light, a lighting device, alight source, or a light, such as an LED, are installed in the area #3.For example, the apparatus #1, the apparatus #2, and the apparatus #3may be apparatuses that use a lighting device or a monitor screeninstalled in each seat as a light source.

In Application Example 1, the apparatus #1 existing in the area #1transmits information on the SSID of one or more APs #1 supporting thefirst wireless LAN scheme. The apparatus #2 existing in the area #2transmits information on the SSID of one or more APs #2 supporting thesecond wireless LAN scheme. The apparatus #3 existing in the area #3transmits information on the SSID of one or more APs #3 supporting thethird wireless LAN scheme.

The terminal positioned in each area uses information on the SSID of anAP obtained by receiving a light signal emitted by any of the apparatus#1, the apparatus #2, and the apparatus #3 to establish a connectionwith the AP corresponding to the obtained SSID through a wireless LAN.Specifically, as illustrated in FIG. 34, the terminal #1 positioned inthe area #1 (for example, first class) obtains information on the SSIDof the AP #1 from the apparatus #1 and establishes a wireless connectionwith the AP #1 by using the obtained SSID. Likewise, as illustrated inFIG. 34, the terminal #2 positioned in the area #2 (for example,business class) obtains information on the SSID of the AP #2 from theapparatus #2 and establishes a wireless connection with the AP #2 byusing the obtained SSID. Also, as illustrated in FIG. 34, the terminal#3 positioned in the area #3 (for example, economy class) obtainsinformation on the SSID of the AP #3 from the apparatus #3 andestablishes a wireless connection with the AP #3 by using the obtainedSSID.

Accordingly, in Application Example 1, a terminal positioned in an areaof a higher service class is able to wirelessly communicate with an APassociated with the class at a higher transmission speed. An APassociated with a certain service class supports a wireless LAN schemesupported by an AP associated with a lower class, and thus a terminalpositioned in an area of a higher service class is able to select notonly a high-speed wireless LAN scheme but also an appropriate wirelessLAN scheme among wireless LAN schemes supported by the terminal.

In addition, in Application Example 1, each of the apparatus #1, theapparatus #2, and the apparatus #3 transmits information on an SSID(modulated signal) by using visible light, and thus the terminal capableof receiving the information on the SSID is limited to a terminal withina range where the light signal can be received from each apparatus. Thatis, each of users of terminals positioned in the areas corresponding toservice classes is able to receive a light signal from an apparatusinstalled in the corresponding area (any of the apparatus #1, theapparatus #2, and the apparatus #3) and to receive servicescorresponding to the class of the area. Accordingly, services that varyaccording to a service class (here, wireless communication services ofdifferent transmission speeds) can be provided.

Application Example 2

In Application Example 2, as in Application Example 1, it is assumedthat, as illustrated in FIG. 35, one or more APs #1 supporting the firstwireless LAN scheme are installed in the area #1, one or more APs #2supporting the second wireless LAN scheme are installed in the area #2,and one or more APs #3 supporting the third wireless LAN scheme areinstalled in the area #3. Each AP is associated with the class ofservices provided in the area in which the AP is installed.

It is assumed that the maximum transmission speed of the first wirelessLAN scheme supported by the AP #1 is higher than the maximumtransmission speed of the second wireless LAN scheme supported by the AP#2, and that the maximum transmission speed of the second wireless LANscheme supported by the AP #2 is higher than the maximum transmissionspeed of the third wireless LAN scheme supported by the AP #3. Forexample, in Application Example 2, the first wireless LAN scheme maysupport IEEE 802.11ac, the second wireless LAN scheme may support IEEE802.11n, and the third wireless LAN scheme may support IEEE 802.11a,IEEE 802.11g, and IEEE 802.11b. Note that examples of the standardssupported by the first wireless LAN scheme, the standards supported bythe second wireless LAN scheme, and the standards supported by the thirdwireless LAN scheme are not limited to the above-described standards.

As illustrated in FIG. 35, one or more apparatuses #1, each including avisible light, a lighting device, a light source, or a light, such as anLED, are installed in the area #1. One or more apparatuses #2, eachincluding a visible light, a lighting device, a light source, or alight, such as an LED, are installed in the area #2. One or moreapparatuses #3, each including a visible light, a lighting device, alight source, or a light, such as an LED, are installed in the area #3.For example, the apparatus #1, the apparatus #2, and the apparatus #3are apparatuses that use a lighting device or a monitor screen installedin each seat as a light source.

In Application Example 2, the apparatus #1 existing in the area #1transmits information on the SSID of one or more APs #1 supporting thefirst wireless LAN scheme, and the apparatus #2 transmits information onthe SSID of one or more APs #2 supporting the second wireless LAN schemeand information on the SSID of one or more APs #3 supporting the thirdwireless LAN scheme.

The apparatus #2 existing in the area #2 transmits information on theSSID of one or more APs #2 supporting the second wireless LAN scheme andinformation on the SSID of one or more APs #3 supporting the thirdwireless LAN scheme.

The apparatus #3 existing in the area #3 transmits information on theSSID of one or more APs #3 supporting the third wireless LAN scheme.

The terminal positioned in each area uses information on the SSID of anAP obtained by receiving a light signal emitted by any of the apparatus#1, the apparatus #2, and the apparatus #3 to establish a connectionwith the AP corresponding to the obtained SSID through a wireless LAN.

Specifically, as illustrated in FIG. 35, the terminal #1 positioned inthe area #1 (for example, first class) obtains information on the SSIDof the AP #1, information on the SSID of the AP #2, and information onthe SSID of the AP #3 from the apparatus #1. Subsequently, the terminal#1 positioned in the area #1 establishes a wireless connection with anAP by using at least any one of the information on the SSID of the AP#1, the information on the SSID of the AP #2, and the information on theSSID of the AP #3 that have been obtained.

Likewise, the terminal #2 positioned in the area #2 (for example,business class) obtains information on the SSID of the AP #2 andinformation on the SSID of the AP #3 from the apparatus #2.Subsequently, the terminal #2 positioned in the area #2 establishes awireless connection with an AP by using at least any one of theinformation on the SSID of the AP #2 and the information on the SSID ofthe AP #3 that have been obtained.

The terminal #3 positioned in the area #3 (for example, economy class)obtains information on the SSID of the AP #3 from the apparatus #3.Subsequently, the terminal #3 positioned in the area #3 establishes awireless connection with the AP #3 by using the obtained SSID of the AP#3.

That is, in Application Example 2, a terminal receives, from anapparatus (transmitter) existing in an area where the terminal ispositioned, a light signal including the SSID of the AP associated withthe class of services provided in the area and the SSID of the APassociated with a lower class. Subsequently, the terminal selects the APto be connected based on the SSIDs included in the light signal.

FIG. 36A illustrates an example of a display screen of a terminal whenthe terminal obtains information on the SSID of an AP.

For example, after obtaining information on an AP (SSID) transmitted bythe apparatus #1, the terminal existing in the area #1 (for example,first class) may display a selection window for “first wireless LANscheme”, “second wireless LAN scheme”, and “third wireless LAN scheme”on the screen (display) of the terminal, as illustrated in FIG. 36A.When the user of the terminal selects “first wireless LAN scheme”, theterminal selects an SSID from information on the SSID of one or more APs#1 supporting the first wireless LAN scheme, and establishes aconnection with the AP #1 through a wireless LAN. When the user of theterminal selects “second wireless LAN scheme”, the terminal selects anSSID from information on the SSID of one or more APs #2 supporting thesecond wireless LAN scheme, and establishes a connection with the AP #2through a wireless LAN. When the user of the terminal selects “thirdwireless LAN scheme”, the terminal selects an SSID from information onthe SSID of one or more APs #3 supporting the third wireless LAN scheme,and establishes a connection with the AP #3 through a wireless LAN.

Also, for example, after obtaining information on an AP (SSID)transmitted by the apparatus #2, the terminal existing in the area #2(for example, business class) displays a selection window for “secondwireless LAN scheme” and “third wireless LAN scheme” on the screen(display) of the terminal, as illustrated in FIG. 36A. When the user ofthe terminal selects “second wireless LAN scheme”, the terminal selectsan SSID from information on the SSID of one or more APs #2 supportingthe second wireless LAN scheme, and establishes a connection with the AP#2 through a wireless LAN. When the user of the terminal selects “thirdwireless LAN scheme”, the terminal selects an SSID from information onthe SSID of one or more APs #3 supporting the third wireless LAN scheme,and establishes a connection with the AP #3 through a wireless LAN.

Also, for example, after obtaining information on an AP (SSID)transmitted by the apparatus #3, the terminal existing in area #3 (forexample, economy class) displays a selection window for “third wirelessLAN scheme” on the screen (display) of the terminal, as illustrated inFIG. 36A. When the user of the terminal selects “third wireless LANscheme”, the terminal selects an SSID from information on the SSID ofone or more APs #3 supporting the third wireless LAN scheme, andestablishes a connection with the AP #3 through a wireless LAN.

That is, the user is able to establish a wireless connection between aterminal and an AP by performing a simple operation of selecting awireless LAN scheme displayed on the terminal.

A description has been given above of a case where “first wireless LANscheme”, “second wireless LAN scheme”, and “third wireless LAN scheme”are displayed on the screen of the terminal as illustrated in FIG. 36A.However, it is not necessary that “first wireless LAN scheme”, “secondwireless LAN scheme”, and “third wireless LAN scheme” be actuallydisplayed, and it is sufficient that display related to (correspondingto) the first wireless LAN scheme, display related to (corresponding to)the second wireless LAN scheme, and display related to (correspondingto) the third wireless LAN scheme be performed.

The display on the screen of the terminal is not limited to the exampleillustrated in FIG. 36A. For example, the display of the terminal maydisplay the SSIDs of individual wireless LAN schemes, as illustrated inFIG. 36B. In this case, the SSID of an AP may be selected by the user byinputting the SSID displayed on the screen to an input field (notillustrated) for the SSID.

In this way, in Application Example 2, a terminal positioned in an areaof a higher service class is able to wirelessly communicate with an APassociated with the class at a higher transmission speed. A terminalpositioned in an area of a class of certain services is able to connectto not only an AP associated with the class but also an AP associatedwith a lower class. Thus, a terminal positioned in an area of a higherservice class is able to select not only a high-speed wireless LANscheme but also an appropriate wireless LAN scheme (i.e., AP) amongwireless LAN schemes supported by the terminal.

In addition, in Application Example 2, each of the apparatus #1, theapparatus #2, and the apparatus #3 transmits information on an SSID(modulated signal) by using visible light, and thus the terminal capableof receiving the information on the SSID is limited to a terminal withina range where the light signal can be received from each apparatus. Thatis, each of users of terminals positioned in the areas corresponding toservice classes is able to receive a light signal from an apparatusinstalled in the corresponding area (any of the apparatus #1, theapparatus #2, and the apparatus #3) and to receive servicescorresponding to the class of the area. Accordingly, wireless LANservices that vary according to a service class (here, wirelesscommunication services of different transmission speeds) can beprovided.

In Application Examples 1 and 2, each of the apparatuses #1, #2, and #3may transmit an encryption key for accessing each AP in addition toinformation on an SSID, and may transmit location information on eachapparatus.

In Application Examples 1 and 2, Usage Examples 1 and 2 described belowmay be applied in accordance with a class of services.

Hereinafter, as illustrated in FIG. 37, a communication system in anaircraft includes the apparatuses #1, #2, and #3 and the APs (basestations) #1, #2, and #3 installed in the areas #1, #2, and #3,respectively, and a local server accessible to each AP. The local servermay store, for example, information, content, and the like to beprovided to passengers in the aircraft.

Also, the communication system in the aircraft includes devices (anInternet server, an antenna, and the like) that are used to access theInternet (i.e., an outside network) via a satellite line or a groundstation.

Usage Example 1

In Usage Example 1, when a terminal is connected to the AP #1 by thefirst wireless LAN scheme, the terminal is capable of accessing thelocal server in the aircraft and to access the Internet via a satelliteline.

When the terminal is connected to the AP #2 by the second wireless LANscheme, the terminal is capable of accessing the local server in theaircraft and to access the Internet via the satellite line.

When the terminal is connected to the AP #3 by the third wireless LANscheme, the terminal is capable of accessing the local server in theaircraft and is incapable of accessing the Internet via the satelliteline.

Usage Example 2

In Usage Example 2, when a terminal is connected to the AP #1 by thefirst wireless LAN scheme, the terminal is capable of accessing thelocal server in the aircraft and to access the Internet via thesatellite line.

When the terminal is connected to the AP #2 by the second wireless LANscheme, the terminal is capable of accessing the local server in theaircraft and is incapable of accessing the Internet via the satelliteline.

When the terminal is connected to the AP #3 by the third wireless LANscheme, the terminal is capable of accessing the local server in theaircraft and is incapable of accessing the Internet via the satelliteline.

That is, the range of a network accessible to a terminal varies inaccordance with an AP connected to the terminal, the AP being associatedwith a class of services provided in an area. Specifically, as the rankof a service class associated with an AP wirelessly connected to theterminal increases, the range of a network accessible to the terminalbecomes larger. In this way, as a result of varying the range (the localserver within the aircraft or the Internet) accessible to the terminalin accordance with the AP connected to the terminal, communicationservices that vary in each service class can be provided to the user.

Next, a description will be given of an example of a procedure ofaccessing an AP from a terminal.

<Access Procedure 1>

(1) The terminal obtains information on the SSID (and the encryptionkey) of an AP from any one of the apparatus #1, the apparatus #2, andthe apparatus #3, and attempts to establish a connection with the APthrough a wireless LAN based on the obtained information.

(2-1) After establishing a connection with the AP, the terminalcommunicates with the connected AP.

(2-2) When it is impossible to establish a connection with the AP, theterminal obtains information on the SSID (and the encryption key) ofanother AP and attempts to establish a connection with the AP through awireless LAN based on the obtained information. The other AP is an APthat is installed in the area identical to the area including the APwith which a connection is not established (i.e., an AP associated withthe same class). At this time, the apparatus that emits a light signalincluding information on the SSID may transmit the SSIDs (and theencryption keys) of a plurality of APs associated with the same classregularly or irregularly.

(3-1) After establishing a connection with the AP, the terminalcommunicates with the connected AP.

(3-2) When it is impossible to establish a connection with the AP, theterminal performs an operation similar to that in the procedure (2-2).

<Access Procedure 2>

The terminal recognizes, in advance, the SSID of an AP to which amodulated signal has been transmitted (note that the SSID may be aplurality of SSIDs).

After that, the terminal obtains information on the SSID (and theencryption key) of the AP from any one of the apparatus #1, theapparatus #2, and the apparatus #3.

When the SSID obtained at this time matches the recognized SSID, theterminal establishes a connection with the AP corresponding to the SSIDthrough a wireless LAN.

On the other hand, when the SSID obtained at this time does not matchthe recognized SSID, the terminal obtains information on the SSID (andthe encryption key) of the AP from another apparatus. The other AP is anAP that is installed in the area identical to the area including the APwith which a connection is not established (i.e., an AP associated withthe same class). At this time, the apparatus that emits a light signalincluding information on the SSID may transmit the SSIDs (and theencryption keys) of a plurality of APs associated with the same classregularly or irregularly.

A description has been given of the procedure of accessing the AP fromthe terminal.

After the connection between the terminal and the AP has beenestablished, an authentication process is performed in the terminal whena web browser is started, for example. For example, upon a seat number,a name, a password, and the like being input by the user, the terminalbecomes capable of performing data communication.

As described above, a terminal establishes, based on information on anSSID (and an encryption key) included in a light signal transmitted(emitted) by an apparatus, a connection with one of APs installed inareas corresponding to service classes and obtains information, therebybeing able to safely obtain information via the AP that issafety-guaranteed.

When the user uses the above-described communication system in theaircraft, it is necessary for the user to download an application forperforming visible light communication to the terminal in advance.

For a terminal that has not downloaded the application for performinglight communication, the communication system may include, for example,an apparatus that displays information on the SSIDs (and the encryptionkeys) of APs, which are connection destinations in individual serviceclasses. This apparatus may be carried by a crew member of the aircraft,for example, and may display, for a user of a terminal that has notdownloaded the application for performing light communication, the SSID(and the encryption key) of the AP corresponding to the service class ofthe user.

The embodiments of the present disclosure have been described above.

The configuration in FIG. 5 has been described as an example of acommunication system that performs visible light communication, but theconfiguration of a communication system that performs visible lightcommunication is not limited to the configuration illustrated in FIG. 5.For example, the configuration illustrated in FIG. 38 may be adopted(see, for example, “IEEE 802.11-16/1499r1”). In FIG. 38, a transmissionsignal is not upconverted and is transmitted as a light signal in abaseband. That is, an apparatus that transmits a light signal of thepresent embodiment (i.e., an apparatus including a light source) mayhave the configuration on the transmission side illustrated in FIG. 38,and a terminal that receives the light signal of the present embodimentmay have the configuration on the reception side illustrated in FIG. 38.

Obviously, a plurality of elements of the embodiments or the likedescribed in this specification may be executed in combination.

Each of the embodiments is merely an example. For example, when “amodulation scheme, an error-correction coding scheme (anerror-correction code, code length, code rate, and the like to be used),control information, and the like” are used as an example, “anothermodulation scheme, another error-correction coding scheme (anerror-correction code, code length, coding rate, and the like to beused), other control information, and the like” may also be applied toimplement the embodiments with a similar configuration.

Regarding a modulation scheme, a modulation scheme other than themodulation scheme described in this specification may be used toimplement the embodiments and the like described in this specification.For example, Amplitude Phase Shift Keying (APSK) (for example, 16APSK,64APSK, 128APSK, 256APSK, 1024APSK, 4096APSK, or the like), PulseAmplitude Modulation (PAM) (for example, 4PAM, 8PAM, 16PAM, 64 PAM,128PAM, 256PAM, 1024PAM, 4096PAM, or the like), Phase Shift Keying (PSK)(for example, BPSK, QPSK, 8PSK, 16PSK, 64PSK, 128PSK, 256PSK, 1024PSK,4096PSK or the like), Quadrature Amplitude Modulation (QAM) (forexample, 4QAM, 8QAM, 16QAM, 64QAM, 128QAM, 256QAM, 1024QAM, 4096QAM, orthe like) may be applied, and uniform mapping or non-uniform mapping maybe used in each modulation scheme. A method for arranging 2, 4, 8, 16,64, 128, 256, or 1024 signal points in the I-Q plane (a modulationscheme with 2, 4, 8, 16, 64, 128, 256, or 1024 signal points) is notlimited to the signal point arrangement method of the modulation schemedescribed in this specification.

An apparatus including the radio device described in this specificationmay be, for example, a communication/broadcast apparatus, such as abroadcast station, a base station, an access point, a terminal, or amobile phone, or a communication apparatus, such as a television set, aradio, a terminal, a personal computer, a mobile phone, an access point,or a base station. The radio device described in this specification is adevice having a communication function, and the device may be configuredto be connected to an apparatus that executes an application, such as atelevision set, a radio, a personal computer, or a mobile phone, via acertain interface.

An apparatus including the receiver described in this specification maybe, for example, a communication/broadcast apparatus, such as abroadcast station, a base station, an access point, a terminal, or amobile phone, or a communication apparatus, such as a television set, aradio, a terminal, a personal computer, a mobile phone, an access point,or a base station.

In wireless communication using a radio wave in the present embodiment,symbols other than data symbols, for example, pilot symbols (a preamble,a unique word, a postamble, a reference symbol, and the like), symbolsfor control information, and the like may be arranged in a frame in anymanner. Here, the terms “pilot symbols” and “symbols for controlinformation” are used, but any other terms may be used. The roles ofindividual symbols are important.

A pilot symbol may be, for example, a known symbol modulated by usingPSK modulation in a transmitter/receiver (or a receiver may be able torecognize a symbol transmitted by a transmitter by achievingsynchronization). The receiver performs frequency synchronization, timesynchronization, channel estimation (estimation of channel stateinformation (CSI)) (of each modulated signal), signal detection, and thelike by using this symbol.

A symbol for control information is a symbol for transmittinginformation, other than data (such as an application), which needs to betransmitted to a communication partner for realizing communication (forexample, a modulation scheme, an error-correction coding scheme, and acoding rate of the error-correction coding scheme used forcommunication, setting information in an upper layer, and the like).

The present disclosure is not limited to the foregoing embodiments, andvarious changes can be applied. For example, in each embodiment, adescription is given of the case of a communication apparatus, but theembodiment is not limited thereto. This communication method can beimplemented by software, hardware, or software that cooperates withhardware.

For example, a program that executes the above-described communicationmethod may be stored in a read only memory (ROM) in advance, and theprogram may be operated by a central processing unit (CPU).

The program that executes the above-described communication method maybe stored in a computer-readable storage medium, and the program storedin the storage medium may be recorded on a random access memory (RAM) ofthe computer, so that the computer may operate in accordance with theprogram.

Some or all of the individual functional blocks used in the descriptionof the foregoing embodiments may be implemented as a large scaleintegration (LSI), which is an integrated circuit, and some or all ofthe individual processes described in the foregoing embodiments may becontrolled by a single LSI or a combination of LSIs. The LSI may beconstituted by individual chips, or may be constituted by a single chipincluding some or all of the functional blocks. The LSI may include aninput and an output of data. The LSI may be called an integrated circuit(IC), a system LSI, a super LSI, or an ultra LSI in accordance with thedegree of integration. The technique of circuit integration is notlimited to the LSI, and the circuit integration may be realized by adedicated circuit, a general-purpose processor, or a dedicatedprocessor. After the LSI is manufactured, a field programmable gatearray (FPGA) that is programmable or a reconfigurable processor capableof reconfiguring the connection and setting of the circuit cell in theLSI may be used. The present disclosure may be implemented as digitalprocessing or analog processing. Furthermore, if a circuit integrationtechnology that replaces the LSI emerges from the progress of thesemiconductor technologies or other technologies derived therefrom,integration of the functional blocks may of course be achieved by usingthe technology. Application of biotechnologies or the like is possible.

(Supplement 1)

A description will be given of a communication method for thetransmission device and the receiving device in FIG. 38. The componentsfrom a symbol mapper (Sym.Map) to LEDs in an upper part of FIG. 38constitute the transmission device. The components from a photodiodeunit (Photo-Diode) to a symbol demapper (Sym.DE-Map) in a lower part ofFIG. 38 constitute the receiving device.

First, a description will be given of the configuration of thetransmission device in the upper part of FIG. 38. This transmissiondevice includes a symbol mapper (Sym.Map), a pre-equalizer, an Hermitiansymmetry processing unit (Hermitian Symmetry), an inverse (fast) Fouriertransform unit (IFFT), a parallel/serial and cyclic prefix addition unit(P/S&CP+), a digital-to-analog converter (DAC), and a light source(LEDs).

The symbol mapper (Sym.Map) receives transmission data (bi) as input andperforms mapping based on a modulation scheme, thereby outputting asymbol sequence (ci). The pre-equalizer receives the symbol sequence(ci) as input, performs pre-equalization on the symbol sequence (ci) toreduce an equalization process on the reception side, and outputs thepre-equalized symbol sequence. The Hermitian symmetry processing unit(Hermitian Symmetry) receives the pre-equalized symbol sequence asinput, allocates sub-carriers to the pre-equalized symbol sequence sothat Hermitian symmetry can be ensured, and outputs parallel signals.

The inverse (fast) Fourier transform unit (IFFT) receives the parallelsignals as input, performs inverse (fast) Fourier transform on theparallel signals, and outputs the signals that have undergone inverse(fast) Fourier transform. The parallel/serial and cyclic prefix additionunit (P/S&CP+) receives the signals that have undergone inverse (fast)Fourier transform as input, performs parallel-to-serial conversion, andcyclic prefix addition, and outputs a signal resulting from the signalprocessing.

The digital-to-analog converter (DAC) receives the processed signal asinput, performs digital-to-analog conversion, and outputs an analogsignal. The analog signal is output as a light modulated signal from oneor more light sources, for example, LEDs.

The transmission device in the upper part of FIG. 38 includes thepre-equalizer and the Hermitian symmetry processing unit, but thetransmission device need not necessarily include the pre-equalizer andthe Hermitian symmetry processing unit. That is, the transmission devicethat performs visible light communication does not necessarily performsignal processing in the pre-equalizer and the Hermitian symmetryprocessing unit.

Next, a description will be given of the receiving device in the lowerpart of FIG. 38. This receiving device includes a photodiode, atransimpedance amplifier (TIA), an analog-to-digital converter (ADC), acyclic prefix removal and serial/parallel conversion unit (CP-&S/P), a(fast) Fourier transform unit (FFT), a detection unit (Detection), and asymbol demapper (Sym.DE-Map).

The photodiode receives a light modulated signal as input and performslight-to-current conversion to convert the light signal into a currentsignal. The transimpedance amplifier (TIA) performs impedance conversionand amplification on the current signal output from the photodiode toobtain a voltage signal. The analog-to-digital converter (ADC) performsanalog-to-digital conversion on the voltage signal and outputs a digitalsignal.

The cyclic prefix removal and serial/parallel conversion unit (CP-&S/P)receives the digital signal as input, performs cyclic prefix removal andthen serial-to-parallel conversion, and outputs parallel signals. The(fast) Fourier transform unit (FFT) receives the parallel signals asinput, performs (fast) Fourier transform, and outputs a signal that hasundergone (fast) Fourier transform.

The detection unit (Detection) receives the Fourier-transformed signalas input, performs detection, and outputs a reception symbol sequence.The symbol demapper (Sym.DE-Map) receives the reception symbol sequenceas input, performs demapping, and obtains a reception data sequence.

As described above, with use of the transmission device for transmittinga light modulated signal and the receiving device that receives thelight modulated signal, described as an example using FIG. 38, theindividual embodiments in this specification can be carried outsimilarly.

(Supplement 2)

In the present disclosure, a terminal establishes a wireless connectionwith a base station or an access point of a wireless LAN. The apparatusconnected to the terminal is not limited to the base station or theaccess point of the wireless LAN, and any other apparatus may beconnected to the terminal as long as the apparatus is wirelesslyconnectable. For example, the apparatus may be a base station or a relaystation of a mobile phone or the like. In the present disclosure, adescription has been given of an example in which information on an SSIDis included in a modulated signal, but the SSID is an example and theembodiment is not limited thereto. That is, the identificationinformation included in the modulated signal is not limited to an SSID,and any other information may be included as long as the informationenables the terminal to identify a safe base station to be connected.

The whole or part of software that is necessary to implement thecommunication method described in the present disclosure may bedownloaded by at least one of a field programmable gate array (FPGA) anda central processing unit (CPU) through wireless communication or wiredcommunication. Furthermore, the whole or part of update software may bedownloaded through wireless communication or wired communication. Thedownloaded software may be stored in a storage unit, and at least one ofthe FPGA and the CPU may be operated based on the stored software,thereby executing digital signal processing described in the presentdisclosure.

At this time, an apparatus including at least one of the FPGA and theCPU may establish a wireless or wired connection with a communicationmodem, and the apparatus and the communication modem may implement thecommunication method described in the present disclosure. For example, acommunication apparatus such as a base station, an AP, or a terminaldescribed in this specification may include at least one of the FPGA andthe CPU, and may include an interface for obtaining, from the outside,software for operating at least one of the FPGA and the CPU.Furthermore, the communication apparatus may include a storage unit forstoring software obtained from the outside, and may operate the FPGA orthe CPU based on the stored software, thereby implementing the signalprocessing described in the present disclosure.

A server may provide an application for processing related to thereceiving device, and a terminal may install the application, therebyimplementing the functions of the receiving device described in thisspecification. The application related to a reception process may beprovided to the terminal by connecting the server to the communicationapparatus including the transmission device described in thisspecification via a network. Alternatively, the application related to areception process may be provided to the terminal by connecting theserver to a communication apparatus having another transmission functionvia a network.

Also, a server may provide an application for processing related to thetransmission device, and a communication apparatus may install theapplication, thereby implementing the functions of the transmissiondevice described in this specification. The application related to atransmission process may be provided to the communication apparatus byconnecting the server to another communication apparatus via a network,but another method may also be used.

Software related to a light source included in the transmission device,and software related to a light receiver included in the receivingdevice may be provided by the server. When each of the transmissiondevice and the receiving device obtains necessary software, the lightsource included in the transmission device is able to transmit a lightmodulated signal, and the light receiver included in the receivingdevice is able to receive the light modulated signal.

Furthermore, the transmission device in this specification may have afunction of the server. In this case, an application included in thetransmission device can be provided to another communication apparatusby using certain communication means. The communication apparatus may beable to serve as the receiving device in this specification by using anapplication that has been obtained by downloading it directly orindirectly from the transmission device.

The “lighting unit” and the “light source” in the present disclosure maybe a device that emits light, such as a display or projector fordisplaying an image, a video, an advertisement, or the like, and theemitted light may include a light modulated signal. That is, the“lighting unit” and the “light source” in the present disclosure mayhave a configuration for outputting sound, an image, a video, or asignal other than light, as well as light. In addition, the “lightingunit” and the “light source” may be constituted by a plurality of“lighting units” or “light sources”.

Furthermore, the transmission method used by the communication apparatusthat generates and emits a light modulated signal may be a method otherthan the transmission method described in this specification. The lightmodulated signal may include information other than the informationdescribed in this specification.

The lighting device or light source, such as an LED, may have thefunctions of the transmission device described in this specification.Alternatively, a device that generates a light modulated signal to betransmitted may not include a lighting device or light source, and maybe connected to the lighting device or light source via a certaininterface.

The communication method for the transmission device and the receivingdevice described in this specification is not limited to theabove-described example, and a wireless communication scheme using anyfrequencies, such as frequencies of light, visible light, infraredlight, or ultraviolet light, may be similarly executed. In thedescription given above, an image sensor receives a light modulatedsignal, but a photodiode may be used instead of the image sensor toreceive a light modulated signal. Alternatively, a device other than animage sensor and a photodiode may be used to receive a light modulatedsignal.

In this specification, the term “symbol” is used, for example,“location-or-position-information-related symbol”,“time-information-related symbol”, “SSID-related symbol”,“access-destination-related symbol”, and “encryption-key-relatedsymbol”. However, these symbols need not necessarily be called symbols,but may be called “data”, “information”, “field”, “bit”, or “region” tocarry out the individual embodiments similarly. A term other than“symbol”, “data”, “information”, “field”, “bit”, and “region” may beused. The transmission device may transmit“location-or-position-information-related symbol”,“time-information-related symbol”, “SSID-related symbol”,“access-destination-related symbol”, and “encryption-key-related symbol”by using any symbol configuration. That is, any configuration may beused for transmission as long as“location-or-position-information-related symbol”,“time-information-related symbol”, “SSID-related symbol”,“access-destination-related symbol”, and “encryption-key-related symbol”can be transmitted to a communication partner.

Again, in this specification, in the transmission device including a“light source”, a “lighting unit”, or the like, the “light source” andthe “lighting unit” may be constituted by a plurality of “light sources”and a plurality of “lighting units”, respectively.

In this specification, a description has been given of an encryption keyby which a terminal establishes a wireless connection with a basestation, but the encryption key is not limited to a “encryption key forwireless connection”. For example, it is assumed that the base stationis connected to a network, and the terminal communicates with thenetwork via the base station. At this time, the encryption key may be a“encryption key by which the terminal establishes a connection with thenetwork”. Thus, the light modulated signal described in thisspecification includes information on the “encryption key”. Accordingly,the embodiments described in this specification can be executedsimilarly, and thus the effects described in the embodiments can besimilarly obtained.

The light modulated signal may include at least one of a “encryption keyfor establishing a connection with a base station (for example, anencryption key for an SSID)” and a “encryption key for establishing aconnection with a network”.

A terminal of the present disclosure includes: a light receiver thatreceives a light signal emitted by a transmitter, the light signalincluding an identifier of at least one base station; a data analyzingcircuit that selects one base station based on the identifier of the atleast one base station that is included in the received light signal;and a radio device that establishes a wireless connection with theselected base station by using the identifier of the base station andwirelessly communicates with the base station.

In the terminal of the present disclosure, the base station isassociated with a class among classes of services, as a rank of theclass increases, a maximum transmission speed of a wirelesscommunication scheme supported by the base station associated with theclass increases, the light receiver receives, from the transmitterexisting in an area of a first class, the light signal including theidentifier of a first base station associated with the first class, theradio device establishes a wireless connection with the first basestation by using the identifier included in the light signal, and firstwireless communication schemes supported by the first base stationincludes a second wireless communication scheme supported by a secondbase station associated with a second class, the second class beinglower than the first class.

In the terminal of the present disclosure, the base station isassociated with a class among classes of services, as a rank of theclass increases, a maximum transmission speed of a wirelesscommunication scheme supported by the base station associated with theclass increases, the light receiver receives, from the transmitterexisting in an area of a first class, the light signal including a firstidentifier of a first base station associated with the first class and asecond identifier of a second base station associated with a secondclass, the second class being lower than the first class, and the radiodevice establishes a wireless connection with the base station by usingone of the first identifier and the second identifier included in thelight signal.

The terminal of the present disclosure further includes a displaycircuit that displays the first identifier and the second identifierthat are included in the light signal.

The terminal of the present disclosure further includes a displaycircuit that displays wireless communication schemes supported by thefirst base station and the second base station, respectively having thefirst identifier and the second identifier that are included in thelight signal.

In the terminal of the present disclosure, the base station isassociated with a class among classes of services, and as a rank of theclass associated with the base station that is wirelessly connected tothe terminal increases, a range of a network accessible to the terminalbecomes larger.

In the terminal of the present disclosure, the transmitter and the basestation are installed in an aircraft, the terminal that is wirelesslyconnected to a first base station associated with a first class iscapable of accessing a network within the aircraft and a network outsidethe aircraft, and the terminal that is wirelessly connected to a secondbase station associated with a second class lower than the first classis capable of accessing the network within the aircraft and is incapableof accessing the outside network.

A communication method of the present disclosure includes: receiving alight signal emitted by a transmitter, the light signal including anidentifier of at least one base station; selecting one base stationbased on the identifier of the at least one base station that isincluded in the received light signal; and establishing a wirelessconnection with the selected base station by using the identifier of thebase station and wirelessly communicating with the base station.

INDUSTRIAL APPLICABILITY

An aspect of the present disclosure is useful to a visible lightcommunication system.

REFERENCE SIGNS LIST

-   -   100, 400, 1000, 1400A, 1400B apparatus    -   102, 1404-1, 1404-2 transmitter    -   104, 1406-1, 1406-2 light source    -   150, 450, 1050 terminal    -   151 light receiver    -   153 receiver    -   155 data analyzer    -   157 display    -   453, 2002 radio device    -   470, 2000 base station    -   2001 transmission device

1. A terminal comprising: a light receiver that receives a light signalemitted by a transmitter, the light signal including an identifier of atleast one base station; a data analyzing circuit that selects one basestation based on the identifier of the at least one base station that isincluded in the received light signal; and a radio device thatestablishes a wireless connection with the selected base station byusing the identifier of the base station and wirelessly communicateswith the base station.
 2. The terminal according to claim 1, wherein thebase station is associated with a class among classes of services, as arank of the class increases, a maximum transmission speed of a wirelesscommunication scheme supported by the base station associated with theclass increases, the light receiver receives, from the transmitterexisting in an area of a first class, the light signal including theidentifier of a first base station associated with the first class, theradio device establishes a wireless connection with the first basestation by using the identifier included in the light signal, and firstwireless communication schemes supported by the first base stationincludes a second wireless communication scheme supported by a secondbase station associated with a second class, the second class beinglower than the first class.
 3. The terminal according to claim 1,wherein the base station is associated with a class among classes ofservices, as a rank of the class increases, a maximum transmission speedof a wireless communication scheme supported by the base stationassociated with the class increases, the light receiver receives, fromthe transmitter existing in an area of a first class, the light signalincluding a first identifier of a first base station associated with thefirst class and a second identifier of a second base station associatedwith a second class, the second class being lower than the first class,and the radio device establishes a wireless connection with the basestation by using one of the first identifier and the second identifierincluded in the light signal.
 4. The terminal according to claim 3,further comprising: a display circuit that displays the first identifierand the second identifier that are included in the light signal.
 5. Theterminal according to claim 3, further comprising: a display circuitthat displays wireless communication schemes supported by the first basestation and the second base station, respectively having the firstidentifier and the second identifier that are included in the lightsignal.
 6. The terminal according to claim 1, wherein the base stationis associated with a class among classes of services, and as a rank ofthe class associated with the base station that is wirelessly connectedto the terminal increases, a range of a network accessible to theterminal becomes larger.
 7. The terminal according to claim 6, whereinthe transmitter and the base station are installed in an aircraft, theterminal that is wirelessly connected to a first base station associatedwith a first class is capable of accessing a network within the aircraftand a network outside the aircraft, and the terminal that is wirelesslyconnected to a second base station associated with a second class lowerthan the first class is capable of accessing the network within theaircraft and is incapable of accessing the outside network.
 8. Acommunication method comprising: receiving a light signal emitted by atransmitter, the light signal including an identifier of at least onebase station; selecting one base station based on the identifier of theat least one base station that is included in the received light signal;and establishing a wireless connection with the selected base station byusing the identifier of the base station and wirelessly communicatingwith the base station.